MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Unidentified. Box 1, folder 19. n.d.. https://collections.library.yale.edu/catalog/2017622.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 1, folder 19"])(n.d.)[Unidentified]. https://collections.library.yale.edu/catalog/2017622.