Cornwell C and RC Sickles (1990). “Production Frontiers with Cross-Sectional and Time-Series Variation in Efficiency Levels.” J Econometrics 46: 185-200.
Cornwell C and RC Sickles (1990). “Production Frontiers with Cross-Sectional and Time-Series Variation in Efficiency Levels.” J Econometrics 46: 185-200.