Introduction to GAMS -- Introduction to Data Envelopment Analysis -- Extensions of DEA models -- Non-radial DEA models -- Allocative, cost, technical, revenue, and profit efficiency -- Special cases in DEA -- Productivity change -- Concluding remarks.

Attempts can be found in the DEA literature to identify returns to scale at efficient interior points of the production possibility set on the basis of returns to scale at points of the corresponding reference sets. However, an opposite approach is put forward in this paper, advocating that...