MLA

Eliot, George, 1819-1880. Letter, to her brother Robert Evans. Box 9. No year, Feb 17. https://collections.library.yale.edu/catalog/32368879.

APA, 6th edition

Eliot, George, 1819-1880. (["Box 9"])(No year, Feb 17)[Letter, to her brother Robert Evans]. https://collections.library.yale.edu/catalog/32368879.