MLA

Pound, Ezra, 1885-1972. Solari, Silvio. Box 49, folder 2164. 1921-45. https://collections.library.yale.edu/catalog/17122628.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 49, folder 2164"])(1921-45)[Solari, Silvio]. https://collections.library.yale.edu/catalog/17122628.