MLA

Eliot, George, 1819-1880. Letter, draft. Box 10. 1883 Dec 11. https://collections.library.yale.edu/catalog/10001526.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 10"])(1883 Dec 11)[Letter, draft]. https://collections.library.yale.edu/catalog/10001526.