see Turabian §16.4.1 (pp. 164–166.)
If you are citing the same source multiple times, you may use shortened citations after the first full citation.
20 Long, Art of Biblical History, 95.
21 Long, “Reading the Old Testament,” 102.
22 Branson and Martínez, 160.
23 Klein, Hubbard, and Blomberg, 76.
24 Schultze et al., 189.
Including a shortened title (up to 4 words) for the book or article is only required if necessary for clarity, such as when you cite multiple works by the same author. Likewise, when citing works by different authors with the same last name, you should include each author’s first name or initials in the shortened citations.