MLA

Lees-Milne, James, 1908-1997. Stewart-Jones, Richard. Box 27, folder 1018. 1938-[50s]. https://collections.library.yale.edu/catalog/2007225.

APA, 6th edition

Lees-Milne, James, 1908-1997. (["Box 27, folder 1018"])(1938-[50s])[Stewart-Jones, Richard]. https://collections.library.yale.edu/catalog/2007225.