1) 1972 summary of coal resources in Colorado

Author
Hornbaker, A. L
Series
Special publication volume 3
Publisher
Colorado Geological Survey
Pub. Date
1973.
Language
English

2) 1975 summary of coal resources in Colorado

Author
Hornbaker, A. L
Series
Special publication volume 9
Publisher
Colorado Geological Survey, Department of Natural Resources, State of Colorado
Pub. Date
1976.
Language
English