MLA

Pound, Ezra, 1885-1972. Bronowski, Jacob. Box 6, folder 256. [1930-31?]. https://collections.library.yale.edu/catalog/17122527.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 6, folder 256"])([1930-31?])[Bronowski, Jacob]. https://collections.library.yale.edu/catalog/17122527.