MLA

Pound, Ezra, 1885-1972. Zukofsky, Louis. Box 3, folder 74. 1930 Jan-Jul. https://collections.library.yale.edu/catalog/17078452.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 3, folder 74"])(1930 Jan-Jul)[Zukofsky, Louis]. https://collections.library.yale.edu/catalog/17078452.