MLA

McClintock, Walter, 1870-1949. SF-258. Meadow of Wild Flowers. Prairie on Two Medicine Ridge. Foothills of the Rockies.. Box 146, folder 7698. undated. https://collections.library.yale.edu/catalog/10453843.

APA, 6th edition

McClintock, Walter, 1870-1949. (["Box 146, folder 7698"])(undated)[SF-258. Meadow of Wild Flowers. Prairie on Two Medicine Ridge. Foothills of the Rockies.]. https://collections.library.yale.edu/catalog/10453843.