MLA

Van Vechten, Carl, 1880-1964. Couturier, Marie-Alain. Box 342, folder 4420. 1940 September 26. https://collections.library.yale.edu/catalog/2032126.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 342, folder 4420"])(1940 September 26)[Couturier, Marie-Alain]. https://collections.library.yale.edu/catalog/2032126.