Daraio C and L Simar (2004). “Introducing External Factors in Nonparametric Frontier Models: A Unifying Approach.” in Emrouznejad A and V Podinovski (eds.) Proceedings of DEA2004, Birmingham, UK: 218.
Daraio C and L Simar (2004). “Introducing External Factors in Nonparametric Frontier Models: A Unifying Approach.” in Emrouznejad A and V Podinovski (eds.) Proceedings of DEA2004, Birmingham, UK: 218.