MLA

Pound, Ezra, 1885-1972. Maverick, Lewis. Box 2, folder 41. 1957 Jul-Aug. https://collections.library.yale.edu/catalog/17078447.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 2, folder 41"])(1957 Jul-Aug)[Maverick, Lewis]. https://collections.library.yale.edu/catalog/17078447.