MLA

Pound, Ezra, 1885-1972. Cathay: Autograph ms. and typescript. Box 80, folder 3543. [1942]. https://collections.library.yale.edu/catalog/17430563.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 80, folder 3543"])([1942])[Cathay: Autograph ms. and typescript]. https://collections.library.yale.edu/catalog/17430563.