MLA

Nicholls, Norton, 1741?-1809. Duchess di Castelpagano to Norton Nicholls. Naples. Count Charles Firmian; Wurmbrand. Box 2, folder 168. [1772]. https://collections.library.yale.edu/catalog/17439965.

APA, 6th edition

Nicholls, Norton, 1741?-1809. (["Box 2, folder 168"])([1772])[Duchess di Castelpagano to Norton Nicholls. Naples. Count Charles Firmian; Wurmbrand]. https://collections.library.yale.edu/catalog/17439965.