1. USGS mineral data available at http://minerals.usgs.gov/minerals/ .
2. From International Aluminium Institute statistics available at www.world-aluminium.org/iai/stats/index.asp.
3. P.A. Plunkert and E.D. Sehnke, Aluminum, Bauxite and Alumina Annual Report (Washington, DC: U.S. Bureau of Mines, 1991).
4. S.K. Das et al., JOM, 56(8) (2004), p. 14.
5. Aluminum Association statistics at www.aluminum.org.