MLA

Van Vechten, Carl, 1880-1964. Zweig, Stefan. Box 384, folder 5756. 1939 January 6. https://collections.library.yale.edu/catalog/10675096.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 384, folder 5756"])(1939 January 6)[Zweig, Stefan]. https://collections.library.yale.edu/catalog/10675096.