MLA

Pound, Ezra, 1885-1972. Silver Shirt Legion of America. Box 48, folder 2131. 1934. https://collections.library.yale.edu/catalog/32160334.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 48, folder 2131"])(1934)[Silver Shirt Legion of America]. https://collections.library.yale.edu/catalog/32160334.