MLA

Van Vechten, Carl, 1880-1964. Pollock, Helen Channing. Box 371 | Folder 5278. 1940 January 15. https://collections.library.yale.edu/catalog/10001228.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 371 | Folder 5278"])(1940 January 15)[Pollock, Helen Channing]. https://collections.library.yale.edu/catalog/10001228.