MLA

Marsh, Othniel Charles, 1831-1899. "L" Compositions. Box 48, folder 19. undated. https://collections.library.yale.edu/catalog/32571995.

APA, 6th edition

Marsh, Othniel Charles, 1831-1899. (["Box 48, folder 19"])(undated)["L" Compositions]. https://collections.library.yale.edu/catalog/32571995.