3.
The role of environmental factors in water utilities’ technical efficiency. Empirical evidence from Spanish companies
Andrés J. Picazo-Tadeo;Francisco J. Sáez-Fernández; Francisco González-Gómez
Applied Economics, 1466-4283, Volume 41, Issue 5, First published 2009, Pages 615 – 628
http://www.informaworld.com/smpp/ftinterface~content=a784709974~fulltext=713240930