MLA

Pound, Ezra, 1885-1972. Cantos IX-XII: typescript. Box 70, folder 3148. 1922 Jul. https://collections.library.yale.edu/catalog/16036230.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 70, folder 3148"])(1922 Jul)[Cantos IX-XII: typescript]. https://collections.library.yale.edu/catalog/16036230.