MLA

Van Vechten, Carl, 1880-1964. Macpherson, Kenneth. Box 363, folder 5029. 1934 January 9. https://collections.library.yale.edu/catalog/2065525.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 363, folder 5029"])(1934 January 9)[Macpherson, Kenneth]. https://collections.library.yale.edu/catalog/2065525.