Fried HO, S Yaisawarng and SS Schmidt (1999). “Incorporating the Operating Environment into a Nonparametric Measure of Technical Efficiency.” JPA 12(3): 247-265.
Fried HO, S Yaisawarng and SS Schmidt (1999). “Incorporating the Operating Environment into a Nonparametric Measure of Technical Efficiency.” JPA 12(3): 247-265.