MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Unidentified. Box 1, folder 18. n.d.. https://collections.library.yale.edu/catalog/2017621.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 1, folder 18"])(n.d.)[Unidentified]. https://collections.library.yale.edu/catalog/2017621.