1. Geothermal (groundsource) heat pumps: a world overview;Lund;Geo-Heat Cent. Q. Bull.,2004
2. The advance of geothermal heat pumps-worldwide;Rybach;IEA Heat pump Center News Letter,2008
3. 101 Water and Water Geothermal Source Heat Pump Unit;NR GT,2012
4. 102 Water/air Geothermal Source Heat Pump Unit;NR GT,2012
5. 103 Water-Air Geothermal Heat Source Multi-type Heat Pump Unit;NR GT,2012