MLA

Pound, Ezra, 1885-1972. Galley proofs. Box 71, folder 3185. n.d.. https://collections.library.yale.edu/catalog/16055613.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 71, folder 3185"])(n.d.)[Galley proofs]. https://collections.library.yale.edu/catalog/16055613.