MLA

Van Vechten, Carl, 1880-1964. Dunham, Katherine. Box 90, folder 1554. 1940 May 10. https://collections.library.yale.edu/catalog/2022546.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 90, folder 1554"])(1940 May 10)[Dunham, Katherine]. https://collections.library.yale.edu/catalog/2022546.