MLA

Van Vechten, Carl, 1880-1964. Foss, Martin. Box 348, folder 4614. 1963 April 10. https://collections.library.yale.edu/catalog/2034739.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 348, folder 4614"])(1963 April 10)[Foss, Martin]. https://collections.library.yale.edu/catalog/2034739.