Hallberg, G.R. (1986). "Pre-Wisconsin glacial stratigraphy of the Central Plains region in Iowa, Nebraska, Kansas, and Missouri". Quaternary Science Reviews. 5: 11–15. Bibcode:1986QSRv....5...11H. doi:10.1016/0277-3791(86)90169-1.
Hallberg, G.R. (1986). "Pre-Wisconsin glacial stratigraphy of the Central Plains region in Iowa, Nebraska, Kansas, and Missouri". Quaternary Science Reviews. 5: 11–15. Bibcode:1986QSRv....5...11H. doi:10.1016/0277-3791(86)90169-1.