MLA

Osborn, Sarah, 1714-1796. Memoir. Box 1 | Folder 4. [n.d., but circa 1760]. https://collections.library.yale.edu/catalog/15763575.

APA, 6th edition

Osborn, Sarah, 1714-1796. (["Box 1 | Folder 4"])([n.d., but circa 1760])[Memoir]. https://collections.library.yale.edu/catalog/15763575.