MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Unidentified. Box 3, folder 99. n.d.. https://collections.library.yale.edu/catalog/2018301.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 3, folder 99"])(n.d.)[Unidentified]. https://collections.library.yale.edu/catalog/2018301.