1. BP global. BP Statistical Review of World Energy 2015. BP 2015. 35–36.
2. BP global. BP Energy Outlook to 2035. BP. 2016. 14–17.
3. International Energy Agency. World Energy Outlook 2015. Executive Summary. IEA 2015. 3–5.
4. U.S. Energy Information Administration. Shale in the United States. EIA 2015. 2015. 3-2.
5. U.S. Energy Information Administration. Annual Energy Outlook 2014 with Projections to 2040. EIA 2014; DOE/EIA-0383. 2014. 108–269.