P., M.E.
MLA
Marsh, Othniel Charles, 1831-1899. P., M.E.. Box 25, folder 1029. 1874. https://collections.library.yale.edu/catalog/32564763.
APA, 6th edition
Marsh, Othniel Charles, 1831-1899. (["Box 25, folder 1029"])(1874)[P., M.E.]. https://collections.library.yale.edu/catalog/32564763.