The official manual for citing and editing your writing in Chicago Style
When To Cite
CITE THE INFORMATION IF:
You use or describe specific information you have taken from a source (as Andrea del Verrocio's pupil Leonardo da Vinci studied in a collaborative environment, sometimes even working with Verrocio himself (Shneiderman, 112).)
You refer to a theory or idea from a source (Shneiderman believes that collaborative learning increases positive outcomes(224).
You include any image (picture, table, graph) from a source.
YOU DON'T NEED TO CITE IF:
The information you use is common knowledge (There are two main types of elephants, Asian and African).
The information you use can be easily found and verified by most people (Abraham Lincoln was 56 years old when he was assassinated)
Dräger, Paul. “Circe.” In Brill's New Pauly: Encyclopaedia of the Ancient World, Vol. 3,eds. Hubert Cancik and Helmut Schneider, 347-349.Leiden: Brill, 2002.
Last name of article author, First Middle. “Title of the Article.” In Title of Reference Book, Vol. #,ed. First & last name of first editor and First & Last name of second editor, page ##-##. City of publisher: Name of publisher, year.