MLA

Boswell, James, 1740-1795. "Mathilda" (C 1981). Box 27, folder 672. 1791. https://collections.library.yale.edu/catalog/32501068.

APA, 6th edition

Boswell, James, 1740-1795. (["Box 27, folder 672"])(1791)["Mathilda" (C 1981)]. https://collections.library.yale.edu/catalog/32501068.