MLA

Pound, Ezra, 1885-1972. Musical score (various drafts); holograph. Box 44, folder 992-93. n.d.. https://collections.library.yale.edu/catalog/2018821.

APA, 6th edition

Pound, Ezra, 1885-1972. (["Box 44, folder 992-93"])(n.d.)[Musical score (various drafts); holograph]. https://collections.library.yale.edu/catalog/2018821.