The Chicago NB system is often used in the humanities and provides writers with a system for referencing their sources through footnote or endnote citation in their writing and through bibliography pages. It also offers writers an outlet for commenting on those cited sources. The NB system is most commonly used in the history discipline.
The proper use of the NB system can protect writers from accusations of plagiarism, which is the intentional or accidental uncredited use of source material created by others. Most importantly, properly using the NB system builds credibility by demonstrating accountability to source material. (Purdue Owl)
In the NB system, you should include a note (endnote or footnote) each time you use a source, whether through a direct quote, paraphrase, or summary. Footnotes will be added at the end of the page on which the source is referenced, and endnotes will be compiled at the end of each chapter or at the end of the entire document.
In either case, a superscript number corresponding to a note with the bibliographic information for that source should be placed in the text following the end of the sentence or clause in which the source is referenced.
If a work includes a bibliography, which is typically preferred, then it is not necessary to provide full publication details in notes. However, if a bibliography is not included with a work, the first note for each source should include all relevant information about the source: author’s full name, source title, and facts of publication. If you cite the same source again, or if a bibliography is included in the work, the note need only include the surname of the author, a shortened form of the title (if more than four words), and page number(s). However, in a work that does not include a bibliography, it is recommended that the full citation be repeated when it is first used in a new chapter.
In contrast to earlier editions of CMOS, if you cite the same source two or more times consecutively, CMOS recommends using shortened citations. In a work with a bibliography, the first reference should use a shortened citation which includes the author’s name, the source title, and the page number(s), and consecutive references to the same work may omit the source title and simply include the author and page number. Although discouraged by CMOS, if you cite the same source and page number(s) from a single source two or more times consecutively, it is also possible to utilize the word “Ibid.,” an abbreviated form of the Latin ibidem, which means “in the same place,” as the corresponding note. If you use the same source but a different page number, the corresponding note should use “Ibid.” followed by a comma and the new page number(s).
In the NB system, the footnote or endnote itself begins with the appropriate full-sized number, followed by a period and then a space. (Purdue Owl)
In the NB system, the bibliography provides an alphabetical list of all sources used in a given work. This page, most often titled Bibliography, is usually placed at the end of the work preceding the index. It should include all sources cited within the work and may sometimes include other relevant sources that were not cited but provide further reading.
Although bibliographic entries for various sources may be formatted differently, all included sources (books, articles, websites, etc.) are arranged alphabetically by author’s last name. If no author or editor is listed, the title or, as a last resort, a descriptive phrase may be used.
Though useful, a bibliography is not required in works that provide full bibliographic information in the notes.
Common Elements
All entries in the bibliography will include the author (or editor, compiler, translator), title, and publication information.
Author Names
The author’s name is inverted in the bibliography, placing the last name first and separating the last name and first name with a comma; for example, John Smith becomes Smith, John. If an author is not listed first, this principle applies to compilers, translators, etc.
Titles
Titles of books and journals are italicized. Titles of articles, chapters, poems, etc. are placed in quotation marks.
Publication Information
The year of publication is listed after the publisher or journal name.
Punctuation
In a bibliography, all major elements are separated by periods.
(Purdue Owl)