Kulshreshtha M and JK Parikh (2002). “Study of Efficiency and Productivity Growth in Opencast and Underground Coal Mining in India: A DEA Analysis.” Energy Economics 24(5): 439-453.
Kulshreshtha M and JK Parikh (2002). “Study of Efficiency and Productivity Growth in Opencast and Underground Coal Mining in India: A DEA Analysis.” Energy Economics 24(5): 439-453.