1. Stories from a Heated Earth – Our Geothermal Heritage,1999
2. Direct utilization of geothermal energy 2010 worldwide review;Lund,2010
3. Direct uses of earth heat;Gudmundsson;International Journal of Energy Research,1985
4. The Lindal diagram;Gudmundsson;Geothermal Resources Council Transactions,1985
5. Geothermal development in Iceland 2005–2009;Ragnarsson,2010