MLA

Williams, William Carlos, 1883-1963. Playwrights. Box 18, folder 583. 1941, undated. https://collections.library.yale.edu/catalog/17049528.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 18, folder 583"])(1941, undated)[Playwrights]. https://collections.library.yale.edu/catalog/17049528.