MLA

Van Vechten, Carl, 1880-1964. Hammerstein, Oscar, II. Box 352, folder 4716. 1939 January 18. https://collections.library.yale.edu/catalog/2036270.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 352, folder 4716"])(1939 January 18)[Hammerstein, Oscar, II]. https://collections.library.yale.edu/catalog/2036270.