MLA

Van Vechten, Carl, 1880-1964. Selwart, Tonio. Box 375, folder 5394. 1932 September 21. https://collections.library.yale.edu/catalog/10052300.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 375, folder 5394"])(1932 September 21)[Selwart, Tonio]. https://collections.library.yale.edu/catalog/10052300.