MLA

Boswell, James, 1740-1795. Voltaire, François Marie Arouet de: engraved portrait (P 166). Box 65, folder 1353. n.d.. https://collections.library.yale.edu/catalog/32501368.

APA, 6th edition

Boswell, James, 1740-1795. (["Box 65, folder 1353"])(n.d.)[Voltaire, François Marie Arouet de: engraved portrait (P 166)]. https://collections.library.yale.edu/catalog/32501368.