MLA

Pound, Ezra, 1885-1972. Cambridge Left: typescript. Box 69, folder 3093. n.d.. https://collections.library.yale.edu/catalog/17122660.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 69, folder 3093"])(n.d.)[Cambridge Left: typescript]. https://collections.library.yale.edu/catalog/17122660.