MLA

Van Vechten, Carl, 1880-1964. Beaton, Cecil. Box 335, folder 4208. 1937 December 7. https://collections.library.yale.edu/catalog/2030533.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 335, folder 4208"])(1937 December 7)[Beaton, Cecil]. https://collections.library.yale.edu/catalog/2030533.