The first time a source is cited in your paper, the corresponding note should include all relevant source information. However, to reduce the overall bulk of publications which use footnotes or endnotes, subsequent usage of that source only requires you to use a shortened version of that citation. Short form information should include the author’s last name, a shortened version of the title (if longer than four words), and any other directing information, such as page numbers.
Note: While previous versions of the Chicago Style Guide used "Ibid" to refer to the same source consecutively multiple times, the 17th edition now requests the use of only shortened citations.
Footnote/Endnote Full Citation
1. Newton N. Minow and Craig L. LaMay, Inside the Presidential Debates: Their Improbable Past and Promising Future (Chicago: University of Chicago Press, 2008), 24-25.
2. Michael Pollan, The Omnivore’s Dilemma: A Natural History of Four Meals (New York: Penguin, 2006), 99-100.
Footnote/Endnote Shortened Citation
3. Minow and LaMay, Presidential Debates, 24-25.
4. Pollan, Omnivore’s Dilemma, 99-100.