MLA

Van Vechten, Carl, 1880-1964. Waters, Ethel. Box 107, folder 1963. 1939 February 19. https://collections.library.yale.edu/catalog/2028430.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 107, folder 1963"])(1939 February 19)[Waters, Ethel]. https://collections.library.yale.edu/catalog/2028430.