– International Ground Source Heat Pump Association
www.igshpa.okstate.edu

– Geothermal Heat Pump Consortium
www.geoexchange.us

– U.S. Department of Energy Energy Efficiency and Renewable Energy
www.eere.energy.gov

– Geo-Heat Center
geoheat.oit.edu

– National Renewable Energy Laboratory
www.nrel.gov

www.waterfurnace.com