2000 resource assessment of selected coal beds and zones in the Northern and Central Appalachian Basin coal regions

[Reston, VA] : U.S. Geological Survey, 2001
Version 1.0.

1999 resource assessment of selected tertiary coal beds and zones in the northern Rocky Mountains and Great Plains region

Denver, CO : U.S. Dept. of the Interior, U.S. Geological Survey : USGS Information Services [distributor], 1999
Version 1.1.