1. IEA
, Key world energy statistics, 2014
2. IEA
, Resources to reserves 2013, oil, gas and coal technologies for the energy markets of the future, 2013
3. EIA
, International Energy Outlook, 2013
4. IEA
, World Energy Outlook, 2014
5. IPCC
, Renewable Energy Sources and Climate Change Mitigation, 2012