MLA

Dellenbaugh, Frederick Samuel, 1853-1935. Escalante Monument Spanish Fork Utah. Box 2 | Folder 44. undated. https://collections.library.yale.edu/catalog/2017839.

APA, 6th edition

Dellenbaugh, Frederick Samuel, 1853-1935. (["Box 2 | Folder 44"])(undated)[Escalante Monument Spanish Fork Utah]. https://collections.library.yale.edu/catalog/2017839.