MLA

Van Vechten, Carl, 1880-1964. Saul, Milton. Box 374, folder 5374. 1947 September 19. https://collections.library.yale.edu/catalog/10050846.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 374, folder 5374"])(1947 September 19)[Saul, Milton]. https://collections.library.yale.edu/catalog/10050846.