1. BP Statistical Review of World Energy, June 2011 (http://www.bp.com).
2. BP Statistical Review of World Energy, June 2010 (http://www.bp.com).
3. Renewables 2011 Global Status Report (www.ren21.net).
4. Energy implications of future stabilization of atmospheric CO2 content
5. US Department of Energy, Energy Efficiency & Renewable Energy, 2008 Solar Technologies Market Report.