MLA

Williams, William Carlos, 1883-1963. Dillon, George. Box 5, folder 170. 1940-1941. https://collections.library.yale.edu/catalog/17049470.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 5, folder 170"])(1940-1941)[Dillon, George]. https://collections.library.yale.edu/catalog/17049470.