Chang HH and R Mashruwala (2006). “Was the Bell System a Natural Monopoly? An Application of Data Envelopment Analysis.” Ann Oper Res 145: 251-263.
Chang HH and R Mashruwala (2006). “Was the Bell System a Natural Monopoly? An Application of Data Envelopment Analysis.” Ann Oper Res 145: 251-263.