1. https://www.eia.gov/ U.S. Energy Information Administration, Accessed May 23, 2019.
2. Heating and cooling energy trends and drivers in buildings;Urge-Vorsatz;Renew. Sustain. Energy Rev.,2015
3. https://www.energy.gov/energysaver/heat-and-cool/heat-pump-systems/geothermal-heat-pumps.
4. Geothermal heat pumps: an increasingly successful technology;Huttrer;Renew. Energy,1997
5. 3 ASHRAE Applications Handbook, Chapter 32, Geothermal Energy.