MLA

Williams, William Carlos, 1883-1963. Dudek, Louis. Box 5, folder 180. 1950-1958. https://collections.library.yale.edu/catalog/11254228.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 5, folder 180"])(1950-1958)[Dudek, Louis]. https://collections.library.yale.edu/catalog/11254228.