MLA

Pound, Ezra, 1885-1972. Callaghan, Morley. Box 7, folder 332. [1927-28?]. https://collections.library.yale.edu/catalog/17122531.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 7, folder 332"])([1927-28?])[Callaghan, Morley]. https://collections.library.yale.edu/catalog/17122531.