MLA

Van Vechten, Carl, 1880-1964. Armstrong, Harry. Box 82, folder 1355. 1937 July 15. https://collections.library.yale.edu/catalog/2020271.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 82, folder 1355"])(1937 July 15)[Armstrong, Harry]. https://collections.library.yale.edu/catalog/2020271.