6[1]World Bank, 1992, World Development Report 1992:Development and Environment, Washington, D.C.,USA
7[3]World Bank, 1996, "Handbook on Economic Analysis of Investment Operations", Washington, D.C. , USA
8[3]John P.Holdren,Gretchen C.Daily.The Meaning of Sustainability:Biogeophysical Aspects,Defining and Measuring Sustainability,The Biogeophysical Foundations,1996,New York.