Preliminary report on coal resources of the Wyodak-Anderson coal zone, Powder River Basin, Wyoming and Montana [electronic resource] / by Margaret S. Ellis ... [et al.].
Imprint
[Reston, Va.] : U.S. Dept. of the Interior, U.S. Geological Survey, [1998]
"The National Coal Resource Assessment (NCRA) project by the U.S. Geological Survey is designed to assess U.S. coal with the greatest potential for development in the next 20-30 years"--P. 4.