MLA

Nicholls, Norton, 1741?-1809. Norton Nicholls to Jane Floyer Nicholls. Chiavenna. Concerns Bern, Switzerland. Box 1, folder 123. 1771 Oct 2. https://collections.library.yale.edu/catalog/17439920.

APA, 6th edition

Nicholls, Norton, 1741?-1809. (["Box 1, folder 123"])(1771 Oct 2)[Norton Nicholls to Jane Floyer Nicholls. Chiavenna. Concerns Bern, Switzerland]. https://collections.library.yale.edu/catalog/17439920.