Wikipedia:Citing sources

A citation, or reference,^{[note 1]} uniquely identifies a source of information, e.g.:

This page documents an English Wikipedia content guideline.

Editors should generally follow it, though exceptions may apply. Substantive edits to this page should reflect consensus.

Shortcuts

This page in a nutshell: Cite reliable sources. You can add a citation by selecting the

button at the top of the editing box. In markup, you can add a citation manually using ref tags. More elaborate and useful ways to cite sources are detailed below.

Ritter, R. M. (2003). The Oxford Style Manual. Oxford University Press. p. 1. ISBN 978-0-19-860564-5.

Wikipedia's verifiability policy requires inline citations for any material challenged or likely to be challenged, and for all quotations, anywhere in article space.

This page explains how to place and format both parts of the citation. A citation or reference in an article usually has two parts. In the first part, each section of text that is either based on, or quoted from, an outside source is marked as such with an inline citation. This is usually displayed as a superscript footnote number: ^[1] The second necessary part of the citation or reference is the list of full references, which provides complete, formatted detail about the source, so that anyone reading the article can find it and verify it.

Each article should use one citation method or style throughout. If an article already has citations, preserve consistency by using that method or seek consensus on the talk page before changing it .

While you should try to write citations correctly, what matters most is that you provide enough information to identify the source. Others will improve the formatting if needed. See: Help:Referencing for beginners for a brief introduction on how to add references using the source editor and The Visual Editor user guide for an automatic way to format citations in Wikipedia.

Citation types

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An inline citation means any citation added close to the material it supports, for example after the sentence or paragraph, normally in the form of a footnote.
In-text attribution involves adding the source of a statement to the article text, such as Rawls argues that X.^[5] This is done whenever a writer or speaker should be credited, such as with quotations, close paraphrasing, or statements of opinion or uncertain fact. The in-text attribution does not give full details of the source – this is done in a footnote in the normal way. See In-text attribution below.
A general reference is a citation that supports content, but is not linked to any particular piece of material in the article through an inline citation. General references are usually listed at the end of the article in a References section. They are usually found in underdeveloped articles, especially when all article content is supported by a single source. They may also be listed in more developed articles as a supplement to inline citations.

Short and full citations

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A full citation fully identifies a reliable source and, where applicable, the place in that source (such as a page number) where the information in question can be found. For example: Rawls, John. A Theory of Justice. Harvard University Press, 1971, p. 1. This type of citation is usually given as a footnote, and is the most commonly used citation method in Wikipedia articles.
A short citation is an inline citation that identifies the place in a source where specific information can be found, but without giving full details of the source. Some Wikipedia articles use it, giving summary information about the source together with a page number. For example, <ref>Rawls 1971, p. 1.</ref>, which renders as Rawls 1971, p. 1.. These are used together with full citations, which are listed in a separate "References" section, or have been provided in a footnote appearing earlier in the article.

Forms of short citations used include author–date referencing (APA style, Harvard style, or Chicago style), and author–title or author–page referencing (MLA style or Chicago style). As before, the list of footnotes is automatically generated in a "Notes" or "Footnotes" section, which immediately precedes the "References" section containing the full citations to the source. Short citations can be written manually, or by using either the {{sfn}} or {{harvnb}} templates or the {{r}} referencing template. The short citations and full citations may be linked so that the reader can click on the short note to find full information about the source. See the template documentation for details and solutions to common problems. For variations with and without templates, see wikilinks to full references. For a set of realistic examples, see these.

This is how short citations look in the edit box:

The Sun is pretty big,<ref>Miller 2005, p. 23.</ref> but the Moon is not so big.<ref>Brown 2006, p. 46.</ref> The Sun is also quite hot.<ref>Miller 2005, p. 34.</ref>

== Notes ==
<references />

== References ==
* Brown, Rebecca (2006). "Size of the Moon", ''Scientific American'', 51 (78).
* Miller, Edward (2005). ''The Sun''. Academic Press.

This is how they look in the article:

The Sun is pretty big,^[1] but the Moon is not so big.^[2] The Sun is also quite hot.^[3]
Notes

^ Miller 2005, p. 23.

^ Brown 2006, p. 46.

^ Miller 2005, p. 34.

References

Brown, Rebecca (2006). "Size of the Moon", Scientific American, 51 (78).

Miller, Edward (2005). The Sun. Academic Press.

Shortened notes using titles rather than publication dates would look like this in the article:

Notes

^ Miller, The Sun, p. 23.

^ Brown, "Size of the Moon", p. 46.

^ Miller, The Sun, p. 34.

When using manual links it is easy to introduce errors such as duplicate anchors and unused references. The script User:Trappist the monk/HarvErrors will show many related errors. Duplicate anchors may be found by using the W3C Markup Validation Service.

When and why to cite sources

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By citing sources for Wikipedia content you enable users to verify that the cited information is supported by reliable sources – improving the credibility of Wikipedia while showing that the content is not original research. You also help users find additional information on the subject; and by giving attribution you avoid plagiarising the source of your words or ideas.

In particular, sources are required for material that is challenged or likely to be challenged. If reliable sources cannot be found for challenged material, it is likely to be removed from the article. Sources are also required when quoting someone, with or without quotation marks, or closely paraphrasing a source. But the need to cite sources is not limited to those situations: editors are always encouraged to add or improve citations for any information in an article.

Citations are especially desirable for statements about living persons, particularly when the statements are contentious or potentially defamatory. In accordance with the biography of living persons policy, unsourced information of this type is likely to be removed on sight.

Wikilinks are not a reliable source, even if they link to a page that provides information on a given topic. If a section from the wikilinked page is copied or transcluded, sources must still be cited in the sampled section even if the wikilink page already has it cited. Users should beware of copying a section with an unreliable source, or where the Wikipedia article does not accurately reflect the source. The source should be read to ensure it is credible and that the Wikipedia article accurately reflects it before transclusion or copying.

Multimedia

For an image or other media file, details of its origin and copyright status should appear on its file page. Image captions should be referenced as appropriate just like any other part of the article. A citation is not needed for descriptions such as alt text that are verifiable directly from the image itself, or for text that merely identifies a source (e.g., the caption "Belshazzar's Feast (1635)" for File:Rembrandt-Belsazar.jpg).

When not to cite

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Citations are not used on disambiguation pages (since sourcing for the information given there should be done in the target articles).

Citations are often omitted from the lead section of an article, insofar as the lead summarizes information for which sources are given later in the article, although quotations and controversial statements, particularly if about living persons, should be supported by citations even in the lead. See WP:LEADCITE for more information.

Consecutive cites of the same source

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Per MOS:CITEPUNCT, citations should be placed at the end of the text that they support. Material (e.g., the fact that elephants are mammals) that is repeated multiple times in a paragraph does not require an inline citation for every mention. If you say an elephant is a mammal more than once, provide one only at the first instance. Avoid cluttering text with redundant citations for the same facts, like this:

Elephants are large^[1] land^[2] mammals^[3] ... Elephants' teeth^[4] are very different^[4] from those of most other mammals.^[3]^[4] Unlike most mammals,^[3] which grow baby teeth^[5] and then replace them with a permanent set of adult teeth,^[4] elephants have cycles of tooth^[5] rotation throughout their entire^[6] lives.^[4]

This does not apply to lists or tables, nor does it apply when multiple sources support different parts of a paragraph or passage. Citation requirements for WP:DYK may require a citation to be inserted (for the duration of the DYK listing) even within a passage completely cited to the same sources.^{[note 2]}

Inline citations

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Inline citations allow the reader to associate a given piece of material in an article with the specific reliable source(s) that support it. Inline citations are added using footnotes, long or short.

How to place an inline citation using ref tags

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To create a footnote, use the <ref>...</ref> syntax at the appropriate place in the article text, for example:

Justice is a human invention.<ref>Rawls, John. ''A Theory of Justice''. Harvard University Press, 1971, p. 1.</ref> It ...

which will be displayed as something like:

Justice is a human invention.^[1] It ...

It will also be necessary to generate the list of footnotes (where the citation text is actually displayed); for this, see § How to create the list of citations.

As in the above example, citation markers are normally placed after adjacent punctuation such as periods (full stops) and commas. For exceptions, see the WP:Manual of Style § Punctuation and footnotes. Note also that no space is added before the citation marker. Citations should not be placed within, or on the same line as, section headings.

The citation should be added close to the material it supports, offering text–source integrity. If a word or phrase is particularly contentious, an inline citation may be added next to that word or phrase within the sentence, but it is usually sufficient to add the citation to the end of the clause, sentence, or paragraph, so long as it's clear which source supports which part of the text.

Avoiding clutter

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Inline references can significantly bloat the wikitext in the edit window and can become confusing and difficult to manage. There are two main methods to avoid clutter in the edit window:

Using list-defined references (LDR) by collecting the full citation code in the References section, and then inserting them in the text with a shortened reference tag, for example <ref name="Smith 2001, p99" />.
Inserting short citations (see below) that then refer to a full list of source texts

As with other citation formats, articles should not undergo large-scale conversion between formats without consensus to do so.

Although references defined in the reference list can be modified with the visual editor, they can only be added or removed using the text editor. Note that unused LDR references will result in an error message.

Repeated citations

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For multiple use of the same inline citation or footnote, you can use the named references feature, choosing a name to identify the inline citation, and typing <ref name="name">text of the citation</ref>. Thereafter, the same named reference may be reused any number of times either before or after the defining use by typing the previous reference name, like this: <ref name="name" />. The use of the slash before the > means that the tag is self-closing, and the </ref> used to close other references must not be used in addition.

The text of the name can be almost anything‍—‌apart from being completely numeric. If spaces are used in the text of the name, the text must be placed within double quotes. Placing all named references within double quotes may be helpful to future editors who do not know that rule. To help with page maintenance, it is recommended that the text of the name have a connection to the inline citation or footnote, for example "author year page": <ref name="Smith 2005 p94">text of the citation</ref>.

Use straight quotation marks " to enclose the reference name. Do not use curly quotation marks “”. Curly marks are treated as another character, not as delimiters. The page will display an error if one style of quotation marks is used when first naming the reference, and the other style is used in a repeated reference.

Citing multiple pages of the same source

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When an article cites many different pages from the same source, to avoid the redundancy of many big, nearly identical full citations, most Wikipedia editors use one of these options:

Named references in conjunction with a combined list of page numbers using the |pages= parameter of the {{cite xxx}} templates (can become confusing for large number of pages)
Named references in conjunction with the {{rp}} or {{r}} templates to specify the page
Short citations

The use of ibid., id., or similar abbreviations is discouraged, as they may become broken as new references are added (op. cit. is less problematic in that it should refer explicitly to a citation contained in the article; however, not all readers are familiar with the meaning of the terms). If the use of ibid is extensive, tag the article using the {{ibid}} template.

What information to include

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Listed below is the information that a typical inline citation or general reference will provide, though other details may be added as necessary. This information is included in order to identify the source, assist readers in finding it, and (in the case of inline citations) indicate the place in the source where the information is to be found. (If an article uses short citations, then the inline citations will refer to this information in abbreviated form, as described in the relevant sections above.)

In general, the citation information should be cited as it appears in the original source; exceptions are noted at MOS:CONFORMTITLE, MOS:TMRULES, MOS:NUMERO, and MOS:TE. For example, the album notes from Hurts 2B Human should not be cited as being from the album Hurts to be Human, or an X (formerly Twitter) user named "i😍dogs" should not be cited as "i[love]dogs". Do not use {{sic}}, per WP:QUOTETYPO.

Examples

Books

Citations for books typically include:

name of author(s)
title of book
volume when appropriate
name of publisher
place of publication
date of publication of the edition
chapter or page numbers cited, if appropriate
edition, if not the first edition
ISBN (optional)

Some edited books have individually authored chapters. Citations for these chapters are recommended. They typically include:

name of author(s)
title of the chapter
name of book's editor
name of book and other details as above
chapter number or page numbers for the chapter (optional)

In some instances, the verso of a book's title page may record, "Reprinted with corrections XXXX" or similar, where "XXXX" is a year. This is a different version of a book in the same way that different editions are different versions. Note this in your citation. See § Dates and reprints for further information.

Journal articles

Citations for journal articles typically include:

name of the author(s)
year and sometimes month of publication
title of the article
name of the journal
volume number, issue number, and page numbers (article numbers in some electronic journals)
DOI and/or other identifiers are optional and can often be used in place of a less stable URL (although URLs may also be listed in a journal citation)

Newspaper articles

Citations for newspaper articles typically include:

byline (author's name), if any
title of the article
name of the newspaper in italics
city of publication (if not included in name of newspaper)
date of publication
page number(s) are optional and may be substituted with negative number(s) on microfilm reels

Web pages

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Citations for websites typically include:

URL of the specific web page where the referenced content can be found. When it is impossible to link to the individual document, instructions for performing a search might be given (see e.g. {{Cite DAT}}), or a link to an archived copy provided.
Name of the author(s)
Title of the article
Title or domain name of the website
Publisher, if known
Date of publication
Page number(s) (if applicable)
Date you retrieved (or accessed) the web page (required if the publication date is unknown)

Sound recordings

Citations for sound recordings typically include:

name of the composer(s), songwriter(s), script writer(s) or the like
name of the performer(s)
title of the song or individual track
title of the album (if applicable)
name of the record label
year of release
medium (for example: LP, audio cassette, CD, MP3 file)
approximate time at which event or point of interest occurs, where appropriate

Do not cite an entire body of work by one performer. Instead, make one citation for each work your text relies on.

Film, television, or video recordings

Citations for films, TV episodes, or video recordings typically include:

name of the director
name of the producer, if relevant
names of major performers
the title of a TV episode
title of the film or TV series
name of the studio
year of release
medium (for example: film, videocassette, DVD)
approximate time at which event or point of interest occurs, where appropriate

Wikidata

Wikidata is largely user-generated, and articles should not directly cite Wikidata as a source (just as it would be inappropriate to cite other Wikipedias' articles as sources).

But Wikidata's statements can be directly transcluded into articles; this is usually done to provide external links or infobox data. For example, more than two million external links from Wikidata are shown through the {{Authority control}} template. There has been controversy over the use of Wikidata in the English Wikipedia due to vandalism and its own sourcing. While there is no consensus on whether information from Wikidata should be used at all, there is general agreement that any Wikidata statements that are transcluded need to be just as reliable compared to Wikipedia content. As such, Module:WikidataIB and some related modules and templates filter Wikidata statements not supported by a reference by default; however, other modules and templates, such as Module:Wikidata, do not.

To transclude an item from Wikidata, the QID (Q number) of an item in Wikidata needs to be known. QID can by found by searching for an item by the name or DOI in Wikidata. A book, a journal article, a musical recording, sheet music or any other item can be represented by a structured item in Wikidata.

The {{Cite Q}} template can be used to cite works whose metadata is held in Wikidata, provided the cited work meets Wikipedia's standards. As of December 2020, {{Cite Q}} does not support "last, first" or Vancouver-style author name lists, so it should not be used in articles in which "last, first" or Vancouver-style author names are the dominant citation style.

Other

Identifying parts of a source

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When citing lengthy sources, you should identify which part of a source is being cited.

Books and print articles

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Specify the page number or range of page numbers. Page numbers are not required for a reference to the book or article as a whole. When you specify a page number, it is helpful to specify the version (date and edition for books) of the source because the layout, pagination, length, etc. can change between editions.

If there are no page numbers, whether in ebooks or print materials, then you can use other means of identifying the relevant section of a lengthy work, such as the chapter number, the section title, or the specific headword. In {{cite book}}, the parameters |chapter= or |at= can include this information.

In some works, such as plays and ancient works, there are standard methods of referring to sections, such as "Act 1, scene 2" for plays and Bekker numbers for Aristotle's works. Use these methods whenever appropriate.

Audio and video sources

Specify the time at which the event or other point of interest occurs. Be as precise as possible about the version of the source that you are citing; for example, movies are often released in different editions or "cuts". Due to variations between formats and playback equipment, precision may not be accurate in some cases. However, many government agencies do not publish minutes and transcripts but do post video of official meetings online; generally the subcontractors who handle audio-visual are quite precise.

Links and ID numbers

A citation ideally includes a link or ID number to help editors locate the source. If you have a URL (web page) link, you can add it to the title part of the citation, so that when you add the citation to Wikipedia the URL becomes hidden and the title becomes clickable. To do this, enclose the URL and the title in square brackets—the URL first, then a space, then the title. For example:

''[https://monographs.iarc.fr/ENG/Monographs/vol66/mono66-7.pdf IARC Monographs On The Evaluation Of Carcinogenic Risks To Humans – Doxefazepam]''. International Agency For Research On Cancer (IARC). 66: 97–104. 13–20 February 1996.

For web-only sources with no publication date, the "Retrieved" date (or the date you accessed the web page) should be included, in case the web page changes in the future. For example: Retrieved 15 July 2011 or you can use the access-date parameter in the automatic Wikipedia:refToolbar 2.0 editing window feature.

You can also add an ID number to the end of a citation. The ID number might be an ISBN for a book, a DOI (digital object identifier) for an article or some e-books, or any of several ID numbers that are specific to particular article databases, such as a PMID number for articles on PubMed.

If your source is not available online, it should be available in reputable libraries, archives, or collections. If a citation without an external link is challenged as unavailable, any of the following is sufficient to show the material to be reasonably available (though not necessarily reliable): providing an ISBN or OCLC number; linking to an established Wikipedia article about the source (the work, its author, or its publisher); or directly quoting the material on the talk page, briefly and in context.

Linking to pages in PDF files

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Links to long PDF documents can be made more convenient by taking readers to a specific page with the addition of #page=n to the document URL, where n is the page number. For example, using https://www.domain.com/document.pdf#page=5 as the citation URL displays page five of the document in any PDF viewer that supports this feature. If the viewer or browser does not support it, it will display the first page instead.

Linking to Google Books pages

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Google Books sometimes allows numbered book pages to be linked to directly. Links to specific pages are optional and should only be added when the book is available for preview; they will not work with snippet view. Keep in mind that availability varies by location.^[a]

These can be added in several ways (with and without citation templates):

Rawls, John. A Theory of Justice. Harvard University Press, 1971, p. 18.
Or with a template: Rawls, John (1971). A Theory of Justice. Harvard University Press. p. 18 – via Google Books.
Rawls 1971, p. 18.
Rawls 1971, p. 18.
Rawls 1971, p. 18.
Rawls 1971, 18.

In edit mode, the URL for p. 18 of A Theory of Justice can be entered like this using the {{Cite book}} template:

{{cite book |last=Rawls |first=John |date=1971 |title=A Theory of Justice |url=https://books.google.com/books?id=kvpby7HtAe0C&pg=PA18 |publisher=Harvard University Press |page=18 |via=Google Books}}

or like this, in the first of the above examples, formatted manually:

Rawls, John. [https://books.google.com/books?id=kvpby7HtAe0C&pg=PA18 ''A Theory of Justice'']. Harvard University Press, 1971, p. 18.

When the page number is a Roman numeral, commonly seen at the beginning of books, the URL looks like this for page xvii (Roman numeral 17) of the same book:

https://books.google.com/books?id=kvpby7HtAe0C&pg=PR17

The &pg=PR17 indicates "page, Roman, 17", in contrast to the &pg=PA18, "page, Arabic, 18" the URL given earlier.

You can also link to a tipped-in page, such as an unnumbered page of images between two regular pages. (If the page contains an image that is protected by copyright, it will be replaced by a tiny notice saying "copyrighted image".) The URL for eleventh tipped-in page inserted after page 304 of The Selected Papers of Elizabeth Cady Stanton and Susan B. Anthony, looks like this:

https://books.google.com/books?id=dBs4CO1DsF4C&pg=PA304-IA11

The &pg=PA304-IA11 can be interpreted as "page, Arabic, 304; inserted after: 11".

Note that some templates properly support links only in parameters specifically designed to hold URLs like |url= and |archive-url= and that placing links in other parameters may not link properly or will cause mangled COinS metadata output. However, the |page= and |pages= parameters of all Citation Style 1/Citation Style 2 citation templates, the family of {{sfn}}- and {{harv}}-style templates, as well as {{r}}, {{rp}} and {{ran}} are designed to be safe in this regard as well.

Citer may be helpful.

Users may also link the quotation on Google Books to individual titles, via a short permalink which ends with their related ISBN, OCLC or LCCN numerical code, e.g.: https://books.google.com/books?vid=ISBN0521349931, a permalink to the Google book with the ISBN code 0521349931. For further details, you may see How-to explanation on support.google.com.

Say where you read it

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"Say where you read it" follows the practice in academic writing of citing sources directly only if you have read the source yourself. If your knowledge of the source is secondhand—that is, if you have read Jones (2010), who cited Smith (2009), and you want to use what Smith (2009) said—make clear that your knowledge of Smith is based on your reading of Jones.

When citing the source, write the following (this formatting is just an example):

John Smith (2009). Name of Book I Haven't Seen, Cambridge University Press, p. 99, cited in Paul Jones (2010). Name of Encyclopedia I Have Seen, Oxford University Press, p. 29.

Or if you are using short citations:

Smith (2009), p. 99, cited in Jones (2010), p. 29.

The same principle applies when indicating the source of images and other media files in an article.

Note: The advice to "say where you read it" does not mean that you have to give credit to any search engines, websites, libraries, library catalogs, archives, subscription services, bibliographies, or other sources that led you to Smith's book. If you have read a book or article yourself, that's all you have to cite. You do not have to specify how you obtained and read it.

So long as you are confident that you read a true and accurate copy, it does not matter whether you read the material using an online service like Google Books; using preview options at a bookseller's website like Amazon; through your library; via online paid databases of scanned publications, such as JSTOR; using reading machines; on an e-reader (except to the extent that this affects page numbering); or any other method.

Dates and reprints

Date a book that is identically reprinted or printed-on-demand to the first date in which the edition became available. For example, if an edition of a book was first released in 2005 with an identical reprinting in 2007, date it to 2005. If substantive changes were made in a reprint, sometimes marked on the verso with "Reprinted with corrections", note the edition and append the corrected reprint year to it (e.g. "1st ed. reprinted with corrections 2005").

Editors should be aware that older sources (especially those in the public domain) are sometimes republished with modern publication dates; treat these as new publications. When this occurs and the citation style being used requires it, cite both the new and original publication dates, e.g.:

Darwin, Charles (1964) [1859]. On the Origin of Species (facsimile of 1st ed.). Harvard University Press.

This is done automatically in the {{citation}} and {{cite book}} templates when you use the |orig-date= parameter.

Alternatively, information about the reprint can be appended as a textual note:

Boole, George (1854). An Investigation of the Laws of Thought on Which Are Founded the Mathematical Theories of Logic and Probabilities. Macmillan. Reprinted with corrections, Dover Publications, New York, NY, 1958.

Seasonal publication dates and differing calendar systems

Publication dates, for both older and recent sources, should be written with the goal of helping the reader find the publication and, once found, confirm that the correct publication has been located. For example, if the publication date bears a date in the Julian calendar, it should not be converted to the Gregorian calendar.

If the publication date was given as a season or holiday, such as "Winter" or "Christmas" of a particular year or two-year span, it should not be converted to a month or date, such as July–August or December 25. If a publication provided both seasonal and specific dates, prefer the specific one.

Additional annotation

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In most cases it is sufficient for a citation footnote simply to identify the source (as described in the sections above); readers can then consult the source to see how it supports the information in the article. Sometimes, however, it is useful to include additional annotation in the footnote, for example to indicate precisely which information the source is supporting (particularly when a single footnote lists more than one source – see § Bundling citations and § Text–source integrity, below).

A footnote may also contain a relevant quotation from the source. This is especially helpful when the cited text is long or dense. A quotation allows readers to immediately identify the applicable portion of the reference. Quotes are also useful if the source is not easily accessible. However, caution should be exercised, as always, to avoid copyright violations.

In the case of non-English sources, it may be helpful to quote from the original text and then give an English translation. If the article itself contains a translation of a quote from such a source (without the original), then the original should be included in the footnote. (See the WP:Verifiability § Non-English sources policy for more information.)

Notes and references section

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This section describes how to add footnotes and also describes how to create a list of full bibliography citations to support shortened footnotes.

The first editor to add footnotes to an article must create a dedicated citations section where they are to appear. Any reasonable name may be chosen.^{[note 3]} The most frequent choice is "References". Other options, in diminishing order of popularity, are "Notes", "Footnotes", or "Works cited", although these are more often used to distinguish between multiple end-matter sections or subsections. Several alternate titles ("Sources", "Citations", "Bibliography") may also be used, although each is problematic: "Sources" may be confused with source code in computer related articles or ways to acquire a product; "Citations" may be confused with official awards or a summons to court; "Bibliography" may be confused with a list of printed works by the subject of a biography.

Sometimes more than one section is needed to organize the citations. For example, articles using shortened citations may use one section for full bibliographic citations and a separate section for shortened citations.

A reference section should not be confused with external links or further reading sections, neither of which contain sources that were used to build the article content.

For an example of headings of a notes section, see the article Tezcatlipoca.

General references

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A general reference is a citation to a reliable source that supports content, but is not linked to any particular text in the article through an inline citation. General references are usually listed at the end of the article in a "References" section, and are usually sorted by the last name of the author or the editor. General reference sections are most likely to be found in underdeveloped articles, especially when all article content is supported by a single source. The disadvantage of general references is that text–source integrity is lost, unless the article is very short. They are frequently reworked by later editors into inline citations.

The appearance of a general references section is the same as those given above in the sections on short citations and parenthetical references. If both cited and uncited references exist, their distinction can be highlighted with separate section names, e.g., "References" and "General references".

How to create the list of citations

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With some exceptions discussed below, citations appear in a single section containing only the <references /> tag or the {{Reflist}} template. For example:

== References ==
{{Reflist}}

or

== References ==
<references />

The footnotes will then automatically be listed under that section heading. Each numbered footnote marker in the text is a clickable link to the corresponding footnote, and each footnote contains a caret that links back to the corresponding point in the text.

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Scrolling lists, or lists of citations appearing within a scroll box, should never be used. This is because of issues with readability, browser compatibility, accessibility, printing, and site mirroring.^{[note 4]}

If an article contains a list of general references, this is usually placed in a separate section, titled, for example, "References". This usually comes immediately after the section(s) listing footnotes, if any. (If the general references section is called "References", then the citations section is usually called "Notes".)

Citations in explanatory footnotes

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WP:EXPLNOTESECTWP:EXPLNOTESECT

Explanatory footnotes require citations, like all content. When an article contains both footnoted citations and other (explanatory) footnotes, it is possible (but not necessary) to divide them into two separate lists using footnotes groups. Explanatory footnotes and citations are then placed in separate sections, called (for example) "Notes" and "References", respectively.

They may be written using citations in footnotes (this requires templates such as {{efn}} or {{refn}}).

The Sun is very big.^[1]^[A]

Notes

[A]
The moon is also very big.^[2]

References

[1]
Miller (2002). Size of the Sun.

[2]
Hsu (2003). Size of the Moon.

Explanatory notes and citations can also be mixed, possibly including short citations referring to earlier footnotes or to a section (often called "Bibliography" or similar) where full citation details can be found.

The Sun is very big.^[1]^[2]

References

[1]
Miller 2008.

[2]
The moon is also very big (Hsu 2007).

Bibliography

Hsu (2007). Size of the Moon.

Miller (2008). Size of the Sun.

Duplicate citations

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Combine precisely duplicated full citations. In this context, "precisely duplicated" means having the same content, not necessarily identical strings ("The New York Times" is the same as "NY Times"; different access-dates are not significant). Do not discourage editors, particularly inexperienced ones, from adding duplicate citations when the use of the source is appropriate, because a duplicate is better than no citation. But any editor should feel free to combine them, and doing so is the best practice on Wikipedia.

Citations to different pages or parts of the same source can also be combined (preserving the distinct parts of the citations), as described in Help:References and page numbers. Any method that is consistent with the existing citation style (if any) may be used, or consensus can be sought to change the existing style. Some tools are listed at Help:Citation tools § Duplicate reference finders.

Citation style

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WP:CITESTYLEWP:CITESTYLE

Citations should aim to provide the information listed above. Wikipedia does not have a single house style. Citations within any given article should follow a consistent style, and applicable Wikipedia style guidelines should be followed. A number of citation styles exist, including APA style, ASA style, MLA style, The Chicago Manual of Style, the Vancouver system and Bluebook. Wikipedia merged several formats into Citation Style 1 and Citation Style 2, which are used in citation templates. Nearly any consistent style can be used, except inline parenthetical referencing, so long as that style is consistently applied within a Wikipedia article. For example, the Wikipedia article should use a consistent capitalization style rather than following one of the cited newspapers in using title case for its headlines, another in using sentence case;^{[note 5]} it can, however, have a style that uses title case for all book titles and sentence case for all book chapter titles.

Avoid all-numeric date formats other than YYYY-MM-DD, because of the ambiguity concerning which number is the month and which the day. For example, 2002-06-11 may be used, but not 11/06/2002. The YYYY-MM-DD format should in any case be limited to Gregorian calendar dates where the year is after 1582. Because it could easily be confused with a range of years, the format YYYY-MM (for example: 2002-06) is not used. For more information on the capitalization of cited works, see Wikipedia:Manual of Style/Capital letters § All caps and small caps.

Variation in citation methods

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Editors should not attempt to change an article's established citation style, merely on the grounds of personal preference or to make it match other articles, without first seeking consensus for the change.^{[note 6]}

As with spelling differences, it is normal practice to defer to the style used by the first major contributor or adopted by the consensus of editors already working on the page, unless a change in consensus has been achieved. If the article you are editing is already using a particular citation style, you should follow it; if you believe it is inappropriate for the needs of the article, seek consensus for a change on the talk page. If you are the first contributor to add citations to an article, you may choose whichever style you think best for the article, except inline parenthetical referencing.

An article where all or most of the citations fail to provide needed bibliographic data does not have a consistent citation style, and can be changed freely to insert such data. Such data includes the name of the source, the title of the article or web page consulted, the author (if known), the publication date (if known), and the page numbers (where relevant). The data provided should be sufficient to uniquely identify the source, allow readers to find it, and allow readers to initially evaluate a source without retrieving it.

Generally considered helpful

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WP:CITEVARYESWP:CITEVARYES

The following are standard practice:

improving existing citations by adding missing information, such as by replacing bare URLs with full bibliographic citations: an improvement because it aids verifiability, and fights link rot;
replacing some or all general references with inline citations: an improvement because it provides more verifiable information to the reader, and helps maintain text–source integrity;
imposing one style on an article with inconsistent citation styles (e.g., some of the citations in footnotes and others as parenthetical references): an improvement because it makes the citations easier to understand and edit;
fixing errors in citation coding, including incorrectly used template parameters, and <ref> markup problems: an improvement because it helps the citations to be parsed correctly;
combining duplicate citations (see § Duplicate citations, above);
converting parenthetical referencing to an acceptable referencing style;
replacing opaque named-reference names with conventional ones, such as "Einstein-1905" instead of ":27"; and
making citations added by other editors match the existing style (if any). Do not revert someone else's contribution merely because the citation style doesn't match. If you know how to fix it, then fix it.
correcting the capitalization of titles to consistently use the chosen style for that article, whether that be title case, sentence case, small caps, etc. (but not all caps, per MOS:ALLCAPS). If title case is used, follow Wikipedia conventions (MOS:TITLECAPS) for which words are capitalized. An article may use distinct capitalization styles for different media kinds; for example: all newspaper articles capitalized one way, and all book titles capitalized a different way.

To be avoided

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When an article is already consistent, avoid:

switching between major citation styles or replacing the preferred style of one academic discipline with another's – except when moving away from deprecated styles, such as parenthetical referencing;
adding citation templates to an article that already uses a consistent system without templates, or removing citation templates from an article that uses them consistently;
changing where the references are defined, e.g., moving reference definitions in the reflist to the prose, or moving reference definitions from the prose into the reflist.

Parenthetical referencing

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WP:PARENWP:PAREN

Inline parenthetical referencing is deprecated on Wikipedia.^{[note 7]} This includes short citations in parentheses placed within the article text itself, such as (Smith 2010, p. 1). This does not affect short citations that use <ref> tags, which are not inline parenthetical references; see the section on short citations above for that method. This also does not affect explanatory footnotes. Some editors prefer to minimize the number of layers of footnoting for readability, but some featured articles have three layers of footnote (explanatory note, short cite, and full cite).

This should no longer be used, and should be replaced with footnotes if encountered:

The Sun is pretty big (Miller 2005, p. 1), but the Moon is not so big (Brown 2006, p. 2). The Sun is also quite hot (Miller 2005, p. 3).

References

Brown, R. (2006). "Size of the Moon", Scientific American, 51 (78).
Miller, E. (2005). The Sun, Academic Press.

Handling links in citations

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WP:CITELINKWP:CITELINK

As noted above under "What information to include", it is helpful to include hyperlinks to source material, when available. Here we note some issues concerning these links.

Avoid embedded links

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WP:CS:EMBEDWP:CS:EMBED

Embedded links to external websites should not be used as inline citations, because they are highly susceptible to link rot. That is, links like:[example.com], which is rendered as: , should not be used as a citation. Avoid raw links even if placed between ref tags (e.g. <ref>[example.com]</ref>). Since any citation that supports the preceding text is better than none, do not revert the good-faith addition of partial citations. They should be replaced with more complete, properly formatted citations as soon as possible.

Embedded links should never be used to place external links in the content of an article, like this: "Example Inc. announced their latest product ...".

Convenience links

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WP:CONLINKWP:CONLINK

A convenience link is a link to a copy of your source on a web page provided by someone other than the original publisher or author. For example, a copy of a newspaper article no longer available on the newspaper's website may be hosted elsewhere. When offering convenience links, it is important to be reasonably certain that the convenience copy is a true copy of the original, without any changes or inappropriate commentary, and that it does not infringe the original rights-holders' copyrights. Accuracy can be assumed when the hosting website appears reliable.

For academic sources, the convenience link is typically a reprint provided by an open-access repository, such as the author's university's library or institutional repository. Such green open access links are generally preferable to paywalled or otherwise commercial and unfree sources.

Where several sites host a copy of the material, the site selected as the convenience link should be the one whose general content appears most in line with Wikipedia:Neutral point of view and Wikipedia:Verifiability.

Indicating availability

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WP:INDICATEAVAILWP:INDICATEAVAIL

If your source is not available online, it should be available in libraries, archives, or collections. If a citation without an external link is challenged as unavailable, any of the following is sufficient to show the material to be reasonably available (though not necessarily reliable): providing an ISBN or OCLC number; linking to an established Wikipedia article about the source (the work, its author, or its publisher); or directly quoting the material on the talk page, briefly and in context.

Links to sources

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WP:SOURCELINKSWP:SOURCELINKS

For a source available in hardcopy, microform, and/or online, omit, in most cases, which one you read. While it is useful to cite author, title, edition (1st, 2nd, etc.), and similar information, it generally is not important to cite a database such as ProQuest, EBSCOhost, or JSTOR (see the list of academic databases and search engines) or to link to such a database requiring a subscription or a third party's login. The basic bibliographic information you provide should be enough to search for the source in any of these databases that have the source. However, you may provide the DOI, ISBN, or another uniform identifier, if available. If the publisher offers a link to the source or its abstract that does not require a payment or a third party's login for access, you may provide the URL for that link. If the source only exists online, give the link even if access is restricted (see WP:PAYWALL).

Preventing and repairing dead links

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WP:DEADREFWP:DEADREF

To help prevent dead links, persistent identifiers are available for some sources. Some journal articles have a digital object identifier (DOI); some online newspapers and blogs, and also Wikipedia, have permalinks that are stable. When permanent links aren't available, consider making an archived copy of the cited document when writing the article; on-demand web archiving services such as the Wayback Machine (https://web.archive.org/save) are fairly easy to use (see pre-emptive archiving).

Do not delete a citation merely because the URL is not working. Dead links should be repaired or replaced if possible. If you encounter a dead URL being used as a reliable source to support article content, follow these steps prior to deleting it:

Confirm status: First, check the link to confirm that it is dead and not temporarily down. The online service "Is it down right now?" can help to determine if a site is down.
Check for a changed URL on the same website: Pages are frequently moved to different locations on the same site. The site's error page may have a "Search" box; alternatively, in both the Google and DuckDuckGo search engines – among others – the keyterm "site:" can be used. For instance: site:nytimes.com "the goose is loose".
Check for web archives: If a web page is unavailable, check whether an archived copy exists. Common web archives on Wikipedia include:
- The Internet Archive has over a trillion archived web pages. See Wikipedia:Using the Wayback Machine.
- The UK Government Web Archive (https://www.nationalarchives.gov.uk/webarchive/) preserves 1500 UK central government websites.
If multiple archive dates are available, try to use one that is most likely to contain the page contents as of the |access-date=. If that parameter is not specified, search the article's revision history to determine when the link was added to the article.
For most citation templates, archive locations are entered using the |archive-url=, |archive-date= and |url-status= parameters. The primary link is switched to the archive link when |url-status=dead. This retains the original link location for reference. If the web page now leads to a completely different website, set |url-status=usurped to hide the original website link in the citation.
Note that some archives operate with a delay. Wait before concluding that no archive exists. Dead URLs to reliable sources should normally be tagged with {{dead link|date={{subst:CURRENTMONTHNAME}} {{subst:CURRENTYEAR}}}}, so that you can estimate how long the link has been dead.
Bookmarklets to check common archive sites for archives of the current page:
Archive.org
javascript:void(window.open('https://web.archive.org/web/*/'+location.href))

Mementos interface
javascript:void(window.open('https://www.webarchive.org.uk/mementos/search/'+encodeURIComponent(location.href)+'?referrer='+encodeURIComponent(document.referrer)))
Remove dead convenience links: If the material was published on paper (e.g., academic journal, newspaper article, magazine, book), then the dead URL is not necessary. Simply remove the dead URL, leaving the remainder of the reference intact.
Find a replacement source: Search the web for quoted text, the article title, and parts of the URL. Consider contacting the website/person that originally published the reference and asking them to republish it. Ask other editors for help finding the reference somewhere else, including the user who added the reference. Find a different source that says essentially the same thing as the reference in question.
Remove hopelessly-lost web-only sources: If the source material does not exist offline, and if there is no archived version of the web page (be sure to wait ~24 months), and if you cannot find another copy of the material, then the dead citation should be removed and the material it supports should be regarded as unverified if there is no other supporting citation. If it is material that is specifically required by policy to have an inline citation, then please consider tagging it with {{citation needed}}. It may be appropriate for you to move the citation to the talk page with an explanation, and notify the editor who added the now-dead link.

Text–source integrity

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When using inline citations, it is important to maintain text–source integrity. The point of an inline citation is to allow readers and other editors to see which part of the material is supported by the citation; that point is lost if the citation is not clearly placed. The distance between material and its source is a matter of editorial judgment, but adding text without clearly placing its source may lead to allegations of original research, of violations of the sourcing policy, and even of plagiarism.

Keeping citations close

Editors should exercise caution when rearranging or inserting material to ensure that text–source relationships are maintained. References should not be moved if doing so might break the text–source relationship.

When new text is inserted into a paragraph, make sure it is supported by the existing source or a new source. If a sentence or paragraph is footnoted with a source, adding new material that is not supported by the existing source to it, without a source for the new text, is highly misleading if placed so as to appear that the cited source supports it. For example, when editing text originally reading

The Sun is pretty big.^[1]

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

an edit that does not imply that the new material is supported by the same reference is

The Sun is pretty big.^[1] The Sun is also quite hot.^[2]

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

^ Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Do not add other facts or assertions into a fully cited paragraph or sentence:

N

The Sun is pretty big, but the Moon is not so big.^[1] The Sun is also quite hot.^[2]

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

^ Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Include a source to support the new information. There are several ways to write this, including:

Y

The Sun is pretty big,^[1] but the Moon is not so big.^[2] The Sun is also quite hot.^[3]

Notes

^ Miller, Edward. The Sun. Academic Press, 2005, p. 1.

^ Brown, Rebecca. "Size of the Moon", Scientific American, 51 (78): 46.

^ Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Citation order

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WP:CITEORDERWP:CITEORDER

There is no consensus for a specific ordering of citations, and editors should not edit-war over it, or make mass changes of ordering to suit personal preferences. In particular, references need not be moved solely to maintain the numerical order of footnotes as they appear in the article.

Bundling citations

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Sometimes the article is more readable if multiple citations are bundled into a single footnote. For example, when there are multiple sources for a given sentence, and each source applies to the entire sentence, the sources can be placed at the end of the sentence, like this:^[4]^[5]^[6]^[7] Or they can be bundled into one footnote at the end of the sentence or paragraph, like this:^[4]

Bundling is also useful if the sources each support a different portion of the preceding text, or if the sources all support the same text. Bundling has several advantages:

It avoids the visual clutter of multiple clickable footnotes inside a sentence or paragraph;
It makes it less likely that inline citations will be moved inadvertently when text is re-arranged, because the footnote states clearly which source supports which point.

Keep in mind that there can be some disadvantages as well:

When multiple sources are bundled into a single citation, it can be unclear which source supports which specific point, particularly if the text contains multiple claims.
Readers and editors may need to cross-check all sources in the bundle to verify a single point, increasing the time and effort required for fact-checking.
Bundling can inadvertently suggest that all sources equally support all points in the cited text, which may not always be accurate.
Rearranging or modifying text later can create confusion or errors if the bundled note needs to be updated or split to reflect new changes.
If an additional source is required for one use of the bundle, then adding it to the bundle will add a useless reference to all the others, or else require a new bundle duplicating all the other references, defeating the purpose of bundling.

To concatenate multiple citations for the same content into a single footnote, there are several layouts available, as illustrated below:

The Sun is pretty big, but the Moon is not so big. The Sun is also quite hot.^[1]

Notes

Use {{Unbulleted list citebundle}}:

^
- For the Sun's size, see: Miller, Edward. The Sun. Academic Press, 2005, p. 1.
- For the Moon's size, see: Brown, Rebecca. "Size of the Moon", Scientific American, 2007, 51 (78): 46.
- For the Sun's heat, see: Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Use an inline paragraph:

^ For the Sun's size, see: Miller, Edward. The Sun. Academic Press, 2005, p. 1. For the Moon's size, see: Brown, Rebecca. "Size of the Moon", Scientific American, 2007, 51 (78): 46. For the Sun's heat, see: Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

Use a bullet list:

^ Multiple sources:
- For the Sun's size, see: Miller, Edward. The Sun. Academic Press, 2005, p. 1.
- For the Moon's size, see: Brown, Rebecca. "Size of the Moon", Scientific American, 2007, 51 (78): 46.
- For the Sun's heat, see: Smith, John. The Sun's Heat. Academic Press, 2005, p. 2.

This last approach needs an introductory line like "Multiple sources:" to prevent an unwanted linebreak after the footnote number.

Simply using line breaks to separate list items breaches MOS:Accessibility § Nobreaks: "<br /> line breaks ... should not be used." {{Unbulleted list citebundle}} a.k.a. {{Multiref}} was made specifically for this purpose. Some other templates in the same vein are listed at the disambiguation page Template:Multiple references.

Within a given article only a single layout should generally be used, except that inline may always be appropriate for shortened references, often all for the same statement:

^ For the Sun's size, see: Miller (2005), p. 1; Brown (2007), p. 46; Smith (2005), p. 2.

In-text attribution

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In-text attribution is the attribution inside a sentence of material to its source, in addition to an inline citation after the sentence. In-text attribution may need to be used with direct speech (a source's words between quotation marks or as a block quotation); indirect speech (a source's words modified without quotation marks); and close paraphrasing. It may also be used when loosely summarizing a source's position in your own words, and it should always be used for biased statements of opinion. For certain frequently discussed sources, in-text attribution is always recommended. It avoids inadvertent plagiarism and helps the reader see where a position is coming from. An inline citation should follow the attribution, usually at the end of the sentence or paragraph in question.

For example:

N To reach fair decisions, parties must consider matters as if behind a veil of ignorance.^[2]

Y John Rawls argues that, to reach fair decisions, parties must consider matters as if behind a veil of ignorance.^[2]

Y John Rawls argues that, to reach fair decisions, parties must consider matters as if "situated behind a veil of ignorance".^[2]

When using in-text attribution, make sure it doesn't lead to an inadvertent neutrality violation. For example, the following implies parity between the sources, without making clear that the position of Darwin is the majority view:

N Charles Darwin says that human beings evolved through natural selection, but John Smith writes that we arrived here in pods from Mars.

Y Humans evolved through natural selection, as first explained in Charles Darwin's The Descent of Man, and Selection in Relation to Sex.

Neutrality issues apart, there are other ways in-text attribution can mislead. The sentence below suggests The New York Times has alone made this important discovery:

N According to The New York Times, the Sun will set in the west this evening.

Y The Sun sets in the west each evening.

It is preferable not to clutter articles with information best left to the references. Interested readers can click on the ref to find out the publishing journal:

N In an article published in The Lancet on 20 December 2023, researchers announced the discovery of the new tissue type.^[3]

Y The discovery of this new tissue type was published in 2023.^[3]

N According to the Oxford English Dictionary, the word pocket comes from French.^[4]

Y The word pocket comes from French.^[4]

Simple facts on which reliable sources are in consensus can have inline citations to reliable sources as an aid to the reader, but normally the text itself is best left as a plain statement without in-text attribution:

N Richard Bauer writes in the 6th edition of Introduction to Chemistry that oxygen is the third most abundant element in the universe by mass, after hydrogen and helium.^[4]

Y By mass, oxygen is the third most abundant element in the universe after hydrogen and helium.^[4]

Short and full citations

Multimedia

When not to cite

Consecutive cites of the same source

How to place an inline citation using ref tags

Avoiding clutter

Repeated citations

Citing multiple pages of the same source

What information to include

Examples

Books

Journal articles

Newspaper articles

Web pages

Sound recordings

Film, television, or video recordings

Wikidata

Other

Identifying parts of a source

Books and print articles

Audio and video sources

Links and ID numbers

Linking to pages in PDF files

Linking to Google Books pages

Say where you read it

Dates and reprints

Seasonal publication dates and differing calendar systems

Additional annotation

General references

How to create the list of citations

Citations in explanatory footnotes

Duplicate citations

Variation in citation methods

Generally considered helpful

To be avoided

Parenthetical referencing

Avoid embedded links

Convenience links

Indicating availability

Links to sources

Preventing and repairing dead links

Keeping citations close

Citation order

Bundling citations

Metadata

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