MLA

Kent, Charles, 1823-1902. Advertisement for Edward Kent, "humorous songs and sketches at the piano" (3 copies). Box 4, folder 169. n.d.. https://collections.library.yale.edu/catalog/17417831.

APA, 6th edition

Kent, Charles, 1823-1902. (["Box 4, folder 169"])(n.d.)[Advertisement for Edward Kent, "humorous songs and sketches at the piano" (3 copies)]. https://collections.library.yale.edu/catalog/17417831.