MLA

Erdoes, Richard, 1912-2008. Cowboys. Box 77 | Western History, White. 1976-1986, undated. https://collections.library.yale.edu/catalog/2099494.

APA, 6th edition

Erdoes, Richard, 1912-2008. (["Box 77 | Western History, White"])(1976-1986, undated)[Cowboys]. https://collections.library.yale.edu/catalog/2099494.