MLA

Van Vechten, Carl, 1880-1964. Valentine, William Robert, at the home of Albert C. (Albert Coombs) Barnes , Lower Merion Township, Pennsylvania. Box 378, folder 5540. 1940 February 4. https://collections.library.yale.edu/catalog/10563817.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 378, folder 5540"])(1940 February 4)[Valentine, William Robert, at the home of Albert C. (Albert Coombs) Barnes , Lower Merion Township, Pennsylvania]. https://collections.library.yale.edu/catalog/10563817.