MLA

Marsh, Othniel Charles, 1831-1899. Mitchell, Charles L.. Box 23, folder 938. 1886. https://collections.library.yale.edu/catalog/32563732.

APA, 6th edition

Marsh, Othniel Charles, 1831-1899. (["Box 23, folder 938"])(1886)[Mitchell, Charles L.]. https://collections.library.yale.edu/catalog/32563732.