MLA

Lees-Milne, James, 1908-1997. Sackville-West, Edward. Box 27, folder 1017. 1942. https://collections.library.yale.edu/catalog/2007223.

APA, 6th edition

Lees-Milne, James, 1908-1997. (["Box 27, folder 1017"])(1942)[Sackville-West, Edward]. https://collections.library.yale.edu/catalog/2007223.