McMullen BS and DW Noh (2007). “Accounting for Emissions in the Measurement of Transit Agency Efficiency: A Directional Distance Function Approach.” Transportation Research Part D 12(1): 1-9.
McMullen BS and DW Noh (2007). “Accounting for Emissions in the Measurement of Transit Agency Efficiency: A Directional Distance Function Approach.” Transportation Research Part D 12(1): 1-9.