The Chicago Manual of Style supports two documentation systems. Pick whichever your instructor or publisher requires.

Notes-Bibliography

Used in history, art history and the humanities. Sources are cited in footnotes or endnotes with a corresponding bibliography entry.

Author-Date

Used in the physical, natural and social sciences. Sources are cited in parentheses by author and year, with a reference list at the end.

Tip

Whichever system you choose, be consistent throughout the manuscript.