1. Lorie A. Wagner, “Materials in the Economy- Material Flows, Scarcity, and the Environment,” 2002, U.S. Geological Survey Circular 1221
2. Paul Collier, The Bottom Billion: Why the Poorest Countries are Failing and What Can Be Done About It (Oxford University Press, 2007), 224.
3. United Nations Department of Economic and Social Affairs Population Division: http://esa.un.org
4. Jonathan Clayton, “Mapping Mineral Deposits and Mining Around the Globe.” 11 April 2013, Available at http://raconteur.net /business/mapping-mineral-deposits-and-mining-around-the-globe
5. United Nations (1987). “Report of the World Commission on Environment and Development.” General Assembly Resolution 42/187, 11 December 1987. Available at http://www.un-documents.net /k-001303.htm” (Accessed 28 December 2011)