MLA

Pound, Ezra, 1885-1972. Oppen, George. "21 Poems": typescript. Box 40, folder 930. [1930]. https://collections.library.yale.edu/catalog/17180228.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 40, folder 930"])([1930])[Oppen, George. "21 Poems": typescript]. https://collections.library.yale.edu/catalog/17180228.