MLA

Van Vechten, Carl, 1880-1964. Isherwood, Christopher. Box 354 | Folder 4790. 1939 February 6. https://collections.library.yale.edu/catalog/2054291.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 354 | Folder 4790"])(1939 February 6)[Isherwood, Christopher]. https://collections.library.yale.edu/catalog/2054291.