1. Deep foundations and geothermal energy – a multi-purpose solution;Quick,2007
2. History of International geothermal power plants and geothermal projects in Germany;Quick,2010
3. Development of porous media theories. a historical note: University of California, Los Angeles (UCLA);de Boer;Civil Engineering Newsletter,1991
4. http://www.geothermie.de, as seen on May 2010.
5. http://www.geothermie-unterhaching.de, as seen on May 2010.