MLA

Van Vechten, Carl, 1880-1964. Kubly, Herbert. Box 357, folder 4888. 1956 October 30. https://collections.library.yale.edu/catalog/2055336.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 357, folder 4888"])(1956 October 30)[Kubly, Herbert]. https://collections.library.yale.edu/catalog/2055336.