Final answer:
In Chicago style, cite a thesis with multiple authors by using the last name of the first author followed by 'et al.' and the year of publication in parentheses.
Step-by-step explanation:
In Chicago style, when citing a thesis with multiple authors, you should include the last name of the first author followed by "et al." and the year of publication in parentheses.
For example, if the thesis was written by David H. Barlow, John Smith, and Mary Johnson in 2019, the citation would look like this:
Barlow et al. (2019)