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Elasticity of substitution and technical efficiency : evidence from the US electricity generation
Mugabe, Douglas, (2020)
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)
Cannel coal in the United States
Ashley, George H., (1918)