1. IEA (2012) Statistics database
2. Earth System Research Laboratory. Global Monitoring Division. National Oceanic & Atmospheric Administration. US Department of Commerce
3. IPCC (2008) Fourth assessment report: Climate change 2007 (AR4)
4. IEA (2011) Key world energy statistics
5. GCCSI (2011) The global status of CCS: 2011. Global CCS Institute