MLA

Van Vechten, Carl, 1880-1964. Chagall, Marc. Box 340 | Folder 4370. 1941 July 4. https://collections.library.yale.edu/catalog/2031991.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 340 | Folder 4370"])(1941 July 4)[Chagall, Marc]. https://collections.library.yale.edu/catalog/2031991.