MLA

Pound, Ezra, 1885-1972. Canto 49: typescript. Box 74, folder 3311. n.d.. https://collections.library.yale.edu/catalog/17122678.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 74, folder 3311"])(n.d.)[Canto 49: typescript]. https://collections.library.yale.edu/catalog/17122678.