MLA

Ford, Charles Henri, 1908-2002. Duchamp, Marcel. Box 1, folder 53. 1947 Aug 4. https://collections.library.yale.edu/catalog/17124847.

APA, 6th edition

Ford, Charles Henri, 1908-2002. (["Box 1, folder 53"])(1947 Aug 4)[Duchamp, Marcel]. https://collections.library.yale.edu/catalog/17124847.