MLA

Bullitt, William C. (William Christian), 1891-1967. Roosevelt, Franklin Delano. Box 71, folder 1783 - 1802. 1934-1939. https://collections.library.yale.edu/catalog/10019343.

APA, 6th edition

Bullitt, William C. (William Christian), 1891-1967. (["Box 71, folder 1783 - 1802"])(1934-1939)[Roosevelt, Franklin Delano]. https://collections.library.yale.edu/catalog/10019343.