MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Colorado River. Box 1, folder 7. n.d.. https://collections.library.yale.edu/catalog/2017541.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 1, folder 7"])(n.d.)[Colorado River]. https://collections.library.yale.edu/catalog/2017541.