MLA

Lewis, Sinclair, 1885-1951. Sadow, Morris. Box 49, folder 601. 1936-1948. https://collections.library.yale.edu/catalog/17116550.

APA, 6th edition

Lewis, Sinclair, 1885-1951. (["Box 49, folder 601"])(1936-1948)[Sadow, Morris]. https://collections.library.yale.edu/catalog/17116550.