The Chicago Manual of Style presents two basic documentation systems, the Humanities style (notes and bibliography) and the Author-Date system. Choosing between the two often depends on subject matter and nature of sources cited, as each system is favored by different groups of scholars.
The Humanities style is preferred by many in literature, history, and the arts. This style presents bibliographic information in notes and, often, a bibliography. It accommodates a variety of sources, including esoteric ones less appropriate to the author-date system.
The more concise Author-Date system has long been used by those in the physical, natural, and social sciences. In this system, sources are briefly cited in the text, usually in parentheses, by author’s last name and date of publication. The short citations are amplified in a list of references, where full bibliographic information is provided.
The two dropdown pages provide some common examples of materials cited in both styles. For numerous specific examples, see chapters 16 and 17 of The Chicago Manual of Style, 15th edition.
Online sources that are analogous to print sources (such as articles published in online journals, magazines, or newspapers) should be cited similarly to their print counterparts but with the addition of a URL. Some publishers or disciplines may also require an access date. For online or other electronic sources that do not have a direct print counterpart (such as an institutional Web site or a Weblog), give as much information as you can in addition to the URL.
The Chicago and Turabian styles are nearly identical.
Kate Turabian, the dissertation secretary at the University of Chicago for over 30 years, developed her guide for students and researchers writing papers, theses, and dissertations. Her manual is based on the University of Chicago Press's Manual of Style and departs from it in few places. "Turabian," as her guide is called, synthesizes the rules most important for students' papers and other scholarly research not intended for publication, and omits some of the publishing details and options that "Chicago" provides.
The differences between the Chicago and Turabian styles are mainly seen in how notes are numbered.
In Turabian style, use superscript 1 for endnote and footnote numbers in the text and at the beginning of each note.
In Chicago style, the note number in the text is in parentheses (1) and is followed by a period and space in the note, as in the following example: