1. Metals for a low-carbon society
2. Hertwich E. G., Gibon T., Bouman E. A., Arvesen A., Suh S., Heath G. A., Bergesen J. D., Ramirez A., Vega M. I. and Shi L.,Proc. Natl. Acad. Sci. U.S.A.(2014) DOI: 10.1073/pnas.1312753111.
3. United States Geological Survey (USGS), Data Series 140,Historical statistics for mineral and material commodities in the Unites States (2014 Version).minerals.usgs.gov/minerals/pubs/historical-statistics/.
4. Report:The world at six billion(United Nations (UN)) 1999.
5. Report:World population prospects: The 2012 revision, United Nations (UN), 2013.