9DOYLE J, GREEN tL Efficiency and Cross-Efficiency in DEA.. Derivations, Meanings and Uses [J]. Journal of the Operational Research Society, 1994, 45 (5): 567-578.
10TUNNA J, JOY R, SHU Xinggao, et al. Methodology to Calculate Variable Usage Charges for Control Period 4 [R]. UK: TTCI (UK), Ltd., 2008.
