MLA

Williams, William Carlos, 1883-1963. Portfolio. Box 19, folder 594. 1959-1960. https://collections.library.yale.edu/catalog/17049531.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 19, folder 594"])(1959-1960)[Portfolio]. https://collections.library.yale.edu/catalog/17049531.