MLA

Van Vechten, Carl, 1880-1964. Waters, Ethel. Box 107, folder 1960-1961. 1938 August 28. https://collections.library.yale.edu/catalog/2001943.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 107, folder 1960-1961"])(1938 August 28)[Waters, Ethel]. https://collections.library.yale.edu/catalog/2001943.