1. Geochemical variation in soils in the Piceance Creek basin, western Colorado : a geochemical baseline study of the composition of soils in a major oil-shale area / by Walter E. Dean, Charles D. Ringrose, and Ronald W. Klusman. Dean, Walter E. [Reston, Va.] : United States Department of the Interior, Geological Survey, 1979.Washington : United States Government Printing Office Book Online