MLA

Pound, Ezra, 1885-1972. Autograph ms.. Box 73, folder 3274. n.d.. https://collections.library.yale.edu/catalog/17122667.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 73, folder 3274"])(n.d.)[Autograph ms.]. https://collections.library.yale.edu/catalog/17122667.