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Research Guides

Citing Your Sources

When to Cite

If you quote an author, even if you are only borrowing a single key word, you must tell your reader where you found the information. Using an author’s words exactly as they appear on the page, then, is a direct quotation that always requires a citation.

You also must cite a source

  • if you restate an idea, thesis, or opinion given by an author,
  • if you restate an expert's theory or opinion,
  • if you use facts that are not common knowledge, or
  • if you need to provide an informational or explanatory note.


These restatements of an author’s words, thoughts, or ideas will take the form of either

  • a summary, or
  • a paraphrase (or indirect quotation).

When is it Okay Not to Cite?

Facts that are common knowledge do NOT have to be cited. For example:

The Republicans succeeded in winning the majority in both the House and Senate in the November elections.

AIDS is a disease that is managed but not cured.

Statistics and information that can easily be found in several sources and are not likely to vary from source to source do not have to be cited. For example, the population of the United States is 281 million.

Dictionary definitions that are common knowledge and vary little from source to source do not have to be cited.