MLA

De Morgan, William, 1839-1917. Chapters 1-41, autograph manuscript. Box 6, folder 41-47. circa 1904. https://collections.library.yale.edu/catalog/17467673.

APA, 6th edition

De Morgan, William, 1839-1917. (["Box 6, folder 41-47"])(circa 1904)[Chapters 1-41, autograph manuscript]. https://collections.library.yale.edu/catalog/17467673.