MLA

Van Vechten, Carl, 1880-1964. Baldwin, Ruth. Box 333, folder 4176. 1933 August 23. https://collections.library.yale.edu/catalog/2030232.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 333, folder 4176"])(1933 August 23)[Baldwin, Ruth]. https://collections.library.yale.edu/catalog/2030232.