MLA

Pound, Ezra, 1885-1972. Blast, Poems from: proofs. Box 111, folder 4677. n.d.. https://collections.library.yale.edu/catalog/2054056.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 111, folder 4677"])(n.d.)[Blast, Poems from: proofs]. https://collections.library.yale.edu/catalog/2054056.