MLA

Nicholls, Norton, 1741?-1809. Charles de Bonstetten to Norton Nicholls. Valegres. Concerns B. Tscharner; William Mason. Box 2, folder 207. 1773 Nov 1. https://collections.library.yale.edu/catalog/17440004.

APA, 6th edition

Nicholls, Norton, 1741?-1809. (["Box 2, folder 207"])(1773 Nov 1)[Charles de Bonstetten to Norton Nicholls. Valegres. Concerns B. Tscharner; William Mason]. https://collections.library.yale.edu/catalog/17440004.