Reddy, G.Thirupati. “Efficiency Scores Analysis of Coal Mines Using IRS, DRS and Cross Efficiency Models”. Journal of Advance Research in Mechanical and Civil Engineering (ISSN: 2208-2379), vol. 2, no. 2, Feb. 2015, pp. 01-07, https://doi.org/10.53555/nnmce.v2i2.367.