1. IEA, Key World Energy Statistics 2014 2014 http://www.iea.org/publications/freepublications/publication/keyworld2014.pdf
2. IEA, Key World Energy Statistics 2013 2013 http://www.iea.org/publications/freepublications/publication/KeyWorld2013_FINAL_WEB.pdf
3. Tyndall Centre for Climate Change Research, CO 2 emissions set to reach new 40 billion tonne record high in 2014 2014 http://www.tyndall.ac.uk/communication/news-archive/2014/co2-emissions-set-reach-new-40-billion-tonne-record-high-2014-0
4. USEPA, Climate Change Indicators in the United States 2012 http://www.epa.gov/climatechange/science/indicators/index.html