MLA

Williams, William Carlos, 1883-1963. Four Seas Company. Box 6, folder 214. 1921-1956. https://collections.library.yale.edu/catalog/10980115.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 6, folder 214"])(1921-1956)[Four Seas Company]. https://collections.library.yale.edu/catalog/10980115.