MLA

Van Vechten, Carl, 1880-1964. Benson, Martin. Box 335, folder 4221. 1938 April 27. https://collections.library.yale.edu/catalog/2030749.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 335, folder 4221"])(1938 April 27)[Benson, Martin]. https://collections.library.yale.edu/catalog/2030749.