MLA

Pound, Ezra, 1885-1972. Vittorini, Elio. Box 54, folder 2463. 1943. https://collections.library.yale.edu/catalog/17122647.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 54, folder 2463"])(1943)[Vittorini, Elio]. https://collections.library.yale.edu/catalog/17122647.