MLA

Van Vechten, Carl, 1880-1964. Steegman, Philip. Box 376, folder 5465. 1940 January 11. https://collections.library.yale.edu/catalog/10059098.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 376, folder 5465"])(1940 January 11)[Steegman, Philip]. https://collections.library.yale.edu/catalog/10059098.