MLA

Pound, Ezra, 1885-1972. Heap, Jane. Box 22, folder 954. 1926-40. https://collections.library.yale.edu/catalog/17122572.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 22, folder 954"])(1926-40)[Heap, Jane]. https://collections.library.yale.edu/catalog/17122572.