MLA

Boswell, James, 1740-1795. Lumsden, Charles. Box 99, folder 1795. 1617. https://collections.library.yale.edu/catalog/2033624.

APA, 6th edition

Boswell, James, 1740-1795. (["Box 99, folder 1795"])(1617)[Lumsden, Charles]. https://collections.library.yale.edu/catalog/2033624.