1. United Nation. Document A/RES/55/2: United Nations millennium declaration, September 2000. See also 〈http://www.un.org/millennium/declaration/ares552e.pdf〉.
2. Brown LR. Plan B 2.0. New York: Earth Policy Institute, W.W. Norton & Company; 2006.
3. WWF. Living planet report 2006, October 2006. See also 〈http://www.footprintnetwork.org/newsletters/gfn_blast_0610.html〉.
4. International Energy Agency. Key world energy statistics 2007. See also 〈http://www.iea.org/Textbase/stats/index.asp〉.
5. CETS and DEPS. Vision 21 fossil fuel options for the future, Washington, DC: National Academy Press; 2000. See also 〈http://www.netl.doe.gov/publications/proceedings/01/vision21/vision21-01.html#Forward〉.