You will need to cite each source that you used twice: first in the text of your paper at the exact point where you quote or paraphrase someone else's work. This is called an "in-text citation," "footnote," or "endnote" depending on the style you are using.
You'll be inserting the citation a second time in your list of Bibliography, References, or Works Cited.
Understanding how and why to use citations is essential for giving credit to the appropriate author and avoiding plagiarism. Citations also help your reader locate sources. You need to ask yourself, is it possible for someone to find this information in the future? For example, census statistics would require a citation because your reader could go locate that information again.
The formatting styles most used to cite sources:
Follow the links above for guidelines in each style type.
Your instructor may assign a specific style for you to follow. If so, use the style consistently throughout your paper: in the layout of the paper (margins, line spacing, cover page), in the footnotes/in-text citations and in your final list of references.