1. Physiographic development of the Great Plains;Alden;Geol. Soc. Am. Bull.,1924
2. Physiography and Glacial Geology of Eastern Montana and Adjacent Areas;Alden;U.S. Geol. Surv. Prof. Pap.,1932
3. The prairie surface;Alt,1984
4. Desert plains;Blackwelder;J. Geol.,1931
5. Geomorphology;Chorley,1984