Apogee Interactive Inc.

http://cenhud.apogee.net/geo/

US Department of Energy

http://www.eere.energy.gov/geothermal/

International Ground Source Heat Pump Association

http://www.igshpa.okstate.edu/

Geoexchange Heat Pump Consortium

http://www.geoexchange.org/resources/47-resources/48-what-is-geoexchange.html