1. Jacobs, A. M., and Lineback, J. A., 1969, Glacial geology of the Vandalia, Illinois, region: Illinois Geol. Survey Circ. 442, 23 p.
2. Willman, H. B., and Frye, J. C., 1970, Pleistocene stratigraphy of Illinois: Illinois Geol. Survey Bull. 94, 204 p.