MLA

Nicholls, Norton, 1741?-1809. Leopoldina Stahremberg to Norton Nicholls. n.p. Concerns Florence; Count Wilseck. Box 2, folder 194. [1773]. https://collections.library.yale.edu/catalog/17439991.

APA, 6th edition

Nicholls, Norton, 1741?-1809. (["Box 2, folder 194"])([1773])[Leopoldina Stahremberg to Norton Nicholls. n.p. Concerns Florence; Count Wilseck]. https://collections.library.yale.edu/catalog/17439991.