MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Colorado River. Box 2, folder 57. n.d.. https://collections.library.yale.edu/catalog/2017891.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 2, folder 57"])(n.d.)[Colorado River]. https://collections.library.yale.edu/catalog/2017891.