MLA

Camp, Walter, 1859-1925. Football: training. Box 64, folder 49 | reel 46U. undated. https://collections.library.yale.edu/catalog/10014906.

APA, 6th edition

Camp, Walter, 1859-1925. (["Box 64, folder 49 | reel 46U"])(undated)[Football: training]. https://collections.library.yale.edu/catalog/10014906.