MLA

Eliot, George, 1819-1880. Letter. Box 8. 1885 Feb 23. https://collections.library.yale.edu/catalog/10001338.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 8"])(1885 Feb 23)[Letter]. https://collections.library.yale.edu/catalog/10001338.