1) James Hughes, 2008, Evidence to the Canadian Standing Committee on Environment and Sustainable Development by Head of Climate and Energy: Strategy and Public Sector Division, UK’s Department of Environment, Food, and Rural Affairs (DEFRA)

2) European Union Emission Trading Scheme (EU ETS), http://ec.europa.eu/environment/climat/emission.htm

3) Union of Concerned Scientists, Clean Energy: How Natural Gas Works, http://www.ucsusa.org/clean_energy/fossil_fuels/offmen-how-natural-gas-works.html

4) DTI, UK Energy in Brief – July 2005, page 20, http://www.berr.gov.uk/files/file10738.pdf

5) DTI, UK Energy in Brief – July 2005, page 23, http://www.berr.gov.uk/files/file10738.pdf