MLA

Pound, Ezra, 1885-1972. Printed proofs. Box 78, folder 3432. n.d.. https://collections.library.yale.edu/catalog/17122694.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 78, folder 3432"])(n.d.)[Printed proofs]. https://collections.library.yale.edu/catalog/17122694.