1. Abrate G., Erbette F. and Fraquelli G. 2008. Cost inefficiency or just heterogeneity? An application of stochastic frontier models to the Italian water industry. Higher Education and Research on Mobility Regulation and the Economics of Local Services, Working Paper # 3.
2. Total factor productivity growth in the state road transport undertakings of India: an assessment through MPI approach;Agarwal;Indian Economic Review,2009
3. Stochastic frontier models with multi time-varying individual effects;Ahn;J. Prod. Anal.,2007
4. American Public Transit Association. 2011. Public transportation fact book, 61st Edition. American Public Transit Association, Washington D.C.
5. American Public Transit Association. 2010. Public transportation fact book, 60th Edition. American Public Transit Association, Washington D.C.