MLA

Willis, John, 1957-. Stand with Standing Rock. Box 2 (Oversize), folder 12. undated. https://collections.library.yale.edu/catalog/32576144.

APA, 6th edition

Willis, John, 1957-. (["Box 2 (Oversize), folder 12"])(undated)[Stand with Standing Rock]. https://collections.library.yale.edu/catalog/32576144.