MLA

Marsh, Othniel Charles, 1831-1899. Baldwin, Charles. Box 2, folder 45. 1880. https://collections.library.yale.edu/catalog/32208587.

APA, 6th edition

Marsh, Othniel Charles, 1831-1899. (["Box 2, folder 45"])(1880)[Baldwin, Charles]. https://collections.library.yale.edu/catalog/32208587.