"When to use shortened citations. To reduce the bulk of documentation in works that use footnotes or endnotes, citations of sources already given in full - either in a previous note or in a bibliography that provides complete bibliographic data - should be shortened whenever possible....The short form, as distinct from an abbreviation, should include enough information to remind readers of the full title or to lead them to the appropriate entry in the bibliography" (The Chicago Manual of Style, 18th ed., 13.32).
"Basic Structure of the short form. The most common short form consists of the last name of the author and the main title of the work cited, usually shortened if more than four words" (The Chicago Manual of Style, 18th ed., 13.33).
1. Heather Hendereshot, When the News Broke: Chicago 1968 and the Polarizing of America (University of Chicago Press, 2022), 149.
2. Marco Cavarzere, "History, Politics, and Fiction in Seventeenth-Century Italy: The Case of Baroque Novels," History of Humanities 7, no. 1(2022): 39-40.
Subsequent Footnotes or Endnotes (Shortened)
3. Hendershot, When the News Broke, 165-66.
4. Cavarzere, "Seventeenth-Century Italy," 42.
"Shortened citations versus "ibid." The abbreviation ibid. (from ibidem, "in the same place") usually refers to a single work cited in the note immediately preceding. However, because ibid. can obscure the identity of a source, Chicago recommends instead using shortened citations...Shortened citations generally take up less than a line, meaning that ibid. saves no space, and in electronic formats that link to one note at a time, ibid. risks confusing the reader" (The Chicago Manual of Style, 18th ed., 13.37).
As seen in the examples below, shortened citations are clearer for the reader than the use of ibid and take up no more space:
1. Carson, Silent Spring, 3.
2. Carson, Silent Spring, 18. or 2. Ibid., 18.
3. Carson, Silent Spring, 18. or 3. Ibid.
4. Carson, Silent Spring, 24-26. or 4. Ibid., 24-26.
5. Carson, The Sea Around Us, 401-2.
6. Carson, The Sea Around Us, 433 . or 6. Ibid., 433.
7. Darwin, Origin of Species, 37-38.
8. Carson, The Sea Around Us, 403.
9. Darwin, Origin of Species, 152.
10. Darwin, Origin of Species, 201-2. or 10. Ibid., 201-2.
11. Carson, Silent Spring, 240; The Sea Around Us, 32.
12. Carson, The Sea Around Us, 33.
"To avoid repetition, an author or title alone may be used in successive citations, though the fuller form is usually preferred" (Chicago Manual of Style, 18th ed., 13.37):
1. Carson, Silent Spring, 18.
2. Carson, 18. or 2. Silent Spring, 18.