APA (7th ed.) Citation

Leighton, M. M., Ekblaw, G. E., & Horberg, L. (1948). Physiographic division of Illinois. [publisher not identified].

Chicago Style (17th ed.) Citation

Leighton, Morris M., George Elbert Ekblaw, and Leland Horberg. Physiographic Division of Illinois. Urbana: [publisher not identified], 1948.

MLA (9th ed.) Citation

Leighton, Morris M., et al. Physiographic Division of Illinois. [publisher not identified], 1948.