Chicago Manual of Style
The Chicago citation style is widely used in history. The Turabian citation style is essentially the same as Chicago style, with slight modifications by Kate L. Turabian for the needs of student writers.
For complete information about Chicago style, consult with The Chicago Manual of Style, 17th edition (available at the Ask Here Desk in the Library).
For complete information about Turabian style, consult with A Manual for Writers of Research Papers, Theses, and Dissertations, 9th edition (available at the Ask Here Desk in the Library).