1. Hall, Charles A.S., Robert C. Powers, and William Schoenberg. 2008. Peak oil, EROI, investments and the economy in an uncertain future. In Renewable energy systems: Environmental and energetic issues, ed. D. Pimentel, 113–136. London: Elsevier.
2. Soddy, F. 1926. Wealth, virtual wealth and debt. New York: E.P. Dutton and Co.
3. Tryon, F.G. 1927. An index of consumption of fuels and water power. Journal of the American Statistical Association 22: 271–282.
4. Cottrell, F. 1955. Energy and society. Dutton: Greenwood Press.
5. Georgescu-Roegen, N. 1971. The entropy law and the economic process. Cambridge: Harvard University Press.