1. http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions
2. http://www.erantis.com/events/world/350/index.htm
3. Lal R (2008) Philos Trans R Soc B Biol Sci 363:815
4. Kato SK, Oshima HK, Oota MK (2001) US Patent 6,270,731
5. Hu X, Nawaby AV, Naguib HE, Day M, Ueda K, Liao X (2005) ANTEC technical papers, vol 7. Boston, MA, p 187