At the point of citation in the main text, enter the reference or footnote like this:
[1]
Then, at all the other citation points just enter:
at the end of the article in a "Notes" or "References" section), insert the tag:
Excel For Dummies, First Edition, Hungry Minds, Inc., 1980.
[citation needed] is expanded to "citation needed", http://en.wikipedia.org/wiki/Wikipedia:Citation_templates