MLA

Williams, William Carlos, 1883-1963. Zukofsky, Louis. Box 27, folder 837-852. 1932-1950. https://collections.library.yale.edu/catalog/17426547.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 27, folder 837-852"])(1932-1950)[Zukofsky, Louis]. https://collections.library.yale.edu/catalog/17426547.