MLA

Van Vechten, Carl, 1880-1964. Vanderbilt, Emily "Paddy," and Emily Davies Vanderbilt Thayer Whitfield. Box 381, folder 5657. 1933 September 21. https://collections.library.yale.edu/catalog/10638383.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 381, folder 5657"])(1933 September 21)[Vanderbilt, Emily "Paddy," and Emily Davies Vanderbilt Thayer Whitfield]. https://collections.library.yale.edu/catalog/10638383.