//-->
Elasticity of substitution and technical efficiency : evidence from the US electricity generation
Mugabe, Douglas, (2020)
Cannel coal in the United States
Ashley, George H., (1918)
Domestic coal industry : hearing before the Subcommittee on Natural Resources Development and Production of the Committee on Energy and Natural Resources, United States Senate, 99th Congress, 2nd session ..., May 1, 1986
(1986)