MLA

Williams, William Carlos, 1883-1963. Various friends. Box 71, folder 1496. 1880-1985. https://collections.library.yale.edu/catalog/2009810.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 71, folder 1496"])(1880-1985)[Various friends]. https://collections.library.yale.edu/catalog/2009810.