MLA

Pound, Ezra, 1885-1972. Price, John Milburn. Box 42, folder 1789-1791. 1925-[28?]. https://collections.library.yale.edu/catalog/17122616.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 42, folder 1789-1791"])(1925-[28?])[Price, John Milburn]. https://collections.library.yale.edu/catalog/17122616.