MLA

Pound, Ezra, 1885-1972. Zukofsky, Louis. Box 3, folder 80. 1933-40. https://collections.library.yale.edu/catalog/17428123.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 3, folder 80"])(1933-40)[Zukofsky, Louis]. https://collections.library.yale.edu/catalog/17428123.