Ask yourself the following questions about the words, ideas, or images you're using:
If you answer "yes" to any of the above, cite the source.
The Purdue Owl adds some clarification.
Three of these claims need citations. Match claims with citations. (Which of these are "common knowledge"? Which need attribution?)
A. Booker T. Washington founded the Tuskegee Institute.
B. People often refer to Freudian Psychoanalysis as the "talking cure."
C. Emily Dickinson was not a silent contemplative; she was "a perceptive, critical, self-propelling person working hard in the midst of a busy town and a busy family and taking the measure of both".
D. "Talking cure" was first applied to the work of Dr. Joseph Breuer, a colleague of Freud's in Vienna, by one of his early "hysterical" female patients, who also jokingly referred to the process as "chimney sweeping".
E. When Booker T. Washington addressed an influential audience in New York in 1903, he inspired a donation to the Tuskegee Institute by Andrew Carnegie of $600,000, or the equivalent of about $350 million in today's dollars, as a relative share of GDP.
F. Emily Dickinson lived a very private life in Amherst, Massachusetts for her entire life, from 1830 to 1886.
Freud, S. (1910). The origin and development of psychoanalysis. The American Journal of Psychology, 21(2), 181-218.
Sewall, R.B. (1974). The life of Emily Dickinson, v. 1. New York: Farrar, Straus and Giroux.
Wilson, J. S. (2012, 4 Sept.). Wealthy Americans, meet historically black colleges. Again." The Chronicle of Higher Education 59(11). Biography In Context. Web.
According to the Purdue OWL, you do not need to cite for purposes of credit when:
"Avoiding Plagiarism," Purdue OWL, Retrieved March 20, 2013, http://owl.english.purdue.edu/owl/resource/589/02/
Common knowledge is information that is easily found in numerous sources and considered widely acceptable information. However, what actually constitutes common knowledge can sometimes be difficult to distinguish and will often depend on the audience and discipline. In general:
(i) If a statement can be found in a very general encyclopedia (such as the Encyclopaedia Brittanica), it is considered common knowledge and does not need to be cited. (NOTE: This does not give you carte blanche to copy and paste verbatim text!)
(ii) If a statement makes an interpretation of widely known facts [as in the second example to the left], rather than simply stating them, it's not common knowledge and needs to be cited.
"Academic Integrity Tutorial" [online resource], Boston College, Lynch School of Education, Fall 2012.
Suppose you're a medical researcher writing an article about how antibodies attack foreign objects in the body.
Would you cite basic information about how antibodies are alerted to a potential pathogen?
If you're writing for other medical biologists, probably not. You all learned that while earning your degrees.
Suppose, though, you're actually writing for materials engineers designing artificial joints. Citations would help those engineers understand the basis of authority and find sources of other information. Armed thus, they could envision processes and make decisions about materials. If there were no citations, they'd just have to take one writer's word for it; they wouldn't have enough information to think for themselves.
CAUTION: Yes, your professor is an expert on Elizabethan poetry, and you can assume he or she has more than basic knowledge. Even so, err on the side of citation. Remember, citation has many purposes: one is to clearly mark a boundary between your own ideas and a source's ideas, and in so doing demonstrate your knowledge of citation conventions for course credit.