article{osti_, title = {Area terrace pit coal mining systems: volume 1technical and economic evaluation of terrace pit mining systems. Open file report (final) Sep 1977Jul 1980}, author = {Leonard, F. and Simon, C. and Stoddard, M. and Verma, M. and White, M.}, abstractNote = {This report is principally concerned with the engineering and economic feasibility of area surface coal ...