REFERENCES
- Gordon , R. B. , Bertram , M. and Graedel , T. E. 2006 . Metal stocks and sustainability . Proc.Natl. Acad. Sci. USA , 103 : 1 – 21 .
- Hotelling , H. 1931 . The economics of exhaustible resources . J. Polit. Econ. , 39 : 137 – 175 .
- Lee , T. and Yao , C.-L. 1970 . Abundance of chemical elements in the earth´s crust ant its major tectonic units . Int. Geol. Rev. , 12 : 778 – 786 .
- Nilsson , D. 2002 . Future world demand for major metals , Presented at the World Mining Congress : New Delhi .
- Skinner , B. J. 1976 . A second iron age ahead? . Am. Sci. , 64 : 158 – 169 .
- Simpson , D. R. , Toman , M. A. and Ayres , R. U. 2005 . In scarcity and growth revisited: Natural resources and the environment in the new millennium , Washington, DC : Resources for the Future .
- Svedberg , P. and Tilton , J. E. 2006 . The real, real price of nonrenewable resources: Copper 1870–2000 . World Dev. , 34 : 501 – 519 .
- Tilton , J. E. 2003 . On borrowed time? Assessing the threat of mineral depletion , Washington, DC : Resources for the Future .
- U.S. Geological Survey . 1980 . Principles of a resource/reserve classification for minerals , 831 Washington, , U.S. : Circular .
- 2005 . World metals and minerals review , London : British Geological Survey and Metal Bulletin .