MLA

Lees-Milne, James, 1908-1997. Mitford, Tom. Box 11, folder 535. 1932-33. https://collections.library.yale.edu/catalog/17300581.

APA, 6th edition

Lees-Milne, James, 1908-1997. (["Box 11, folder 535"])(1932-33)[Mitford, Tom]. https://collections.library.yale.edu/catalog/17300581.