MLA

Rudge, Olga, 1895-1996. Pound, Ezra. Box 31, folder 880-881. 1908-72, n.d.. https://collections.library.yale.edu/catalog/17082127.

APA, 6th edition

Rudge, Olga, 1895-1996. (["Box 31, folder 880-881"])(1908-72, n.d.)[Pound, Ezra]. https://collections.library.yale.edu/catalog/17082127.