MLA

Van Vechten, Carl, 1880-1964. Perkins, Julius, Jr.. Box 100 | Folder 1794. 1939 July 22. https://collections.library.yale.edu/catalog/2027100.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 100 | Folder 1794"])(1939 July 22)[Perkins, Julius, Jr.]. https://collections.library.yale.edu/catalog/2027100.