MLA

Van Vechten, Carl, 1880-1964. Bennett, Gwendolyn. Box 2, folder 56. 1926, undated. https://collections.library.yale.edu/catalog/16820216.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 2, folder 56"])(1926, undated)[Bennett, Gwendolyn]. https://collections.library.yale.edu/catalog/16820216.