You do not need to cite common knowledge.
In most citation styles, two parts are needed:
Use the tabs above to learn about these two parts in your chosen citation style.
Use the style recommended by your professor or choose one of the major styles below based on the discipline for your paper:
Widely-known, generally-accepted information that is not attributable to one source.
What is considered common knowledge can be tricky. When in doubt, ask your professor!
1. Cohen, William. "Thomas Jefferson and the Problem of Slavery." Journal of American History 56, no. 3 (1969): 503-26.