1. Energy Demand and Climate Change;Cocks,2009
2. U.S.A. Energy Information Administration, Annual Energy Review 2011, Table 2.1a Energy Consumption Estimates by Sector, Selected Years, 1949–2011, , (February, 2013).
3. Current status of ground source heat pumps and underground thermal energy storage in Europe;Sanner;Geothermics,2003
4. Thermal Energy Storage: Systems and Applications;Dincer,2002
5. See for Geothermal Heat Pump Systems 2005, CIPCO Energy Library.