MLA

Van Vechten, Carl, 1880-1964. Peterson, Jerome Bowers. Box 101, folder 1814. 1939 August 18. https://collections.library.yale.edu/catalog/2027168.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 101, folder 1814"])(1939 August 18)[Peterson, Jerome Bowers]. https://collections.library.yale.edu/catalog/2027168.