MLA

Pound, Ezra, 1885-1972. Zukofsky, Louis. Box 3, folder 72. 1928. https://collections.library.yale.edu/catalog/17428118.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 3, folder 72"])(1928)[Zukofsky, Louis]. https://collections.library.yale.edu/catalog/17428118.