MLA

Van Horn, Erica., and creator. Some Words from That Letter. s.n, 0AD. https://collections.library.yale.edu/catalog/2055132.

APA, 6th edition

Van Horn, E., & creator. (0 C.E.). Some words from that letter [Artists' books, Folded books]. s.n. https://collections.library.yale.edu/catalog/2055132.