Major Citation Style Manuals
Chicago Manual of Style (or Ref Desk Z253.U69 2003)
NOTE: There are two versions outlined in Chicago: A, the humanities style, and B, author-date, preferred by social science and science disciplines.
MLA Handbook for Writers of Research Papers (Ref Desk LB2369.G53 2003)
Publication Manual of the American Psychological Association (Ref Desk BF76.7 .P83 2001)
When to Cite
Academic writing requires that you acknowledge use of the intellectual work of others. These are some of the most common situations that require that you identify and give credit to the work of others:
- A direct quote from a text.
- A direct quote from someone else’s writing about that text.
- A paraphrase of the ideas of another writer.
It is not necessary to give credit for commonly known facts or expressions. 
Why to Cite
The most recent edition of Turabian’s A Manual for Writers of Research Papers, Theses, and Dissertations gives four reasons for citing outside sources used in your writing:
• To give credit
• To assure readers of the accuracy of your facts
• To show readers the research tradition that informs your work
• To help readers follow or extend your research 
Failure to give credit to the ideas of others, whether intentional or not, constitutes plagiarism and is a violation of Reed’s Honor Principle as described in the Reed College Guidebook:
"Academic misconduct is a breach of the principle of proper academic conduct and includes both intentional acts of misrepresenting another's work as one's own as well as unintentional acts that fail to conform to the rules of appropriate attribution and credit. Academic misconduct is a violation of Reed's Honor Principle in its most fundamental form and is contrary to the idea of scholarship."
 Kate L. Turabian, A Manual for Writers of Research Papers, Theses, and Dissertations: Chicago Style for Students and Researchers, 7th ed., revised by Wayne C. Booth et al. (Chicago: University of Chicago Press, 2007), 133-34.