MLA

Pound, Ezra, 1885-1972. Fuller, John Frederick Charles. Box 18, folder 783. 1939-58. https://collections.library.yale.edu/catalog/17122563.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 18, folder 783"])(1939-58)[Fuller, John Frederick Charles]. https://collections.library.yale.edu/catalog/17122563.