Charnes, A., Cooper,W. W. and Rhodes, E. (1978), Measuring the efficiency of decision making units. European Journal of operational Research, 2, 429-444.
 David A.Haas, Frederic H. Murphy. (2003) Compensating for nonhomogeneity in decision making units in data envelopment analysis, 144,530-544.
 Yan, H., wei, Q.L, Hao, G. (2002), DEA models for resource allocation and production input -output estimation. European Journal of operational Research, 136(1), 19-31.