MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Colorado River. Box 4, folder 134. n.d.. https://collections.library.yale.edu/catalog/2025208.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 4, folder 134"])(n.d.)[Colorado River]. https://collections.library.yale.edu/catalog/2025208.