1. ASHRAE handbook – HVAC applications,2007
2. Heat conduction with engineering and geological applications;Ingersoll,1954
3. Kavanaugh SP. Simulation and experimental verification of a vertical ground-coupled heat pump system. Ph.D. dissertation. Stillwater: Oklahoma State University; 1985.
4. Rybach L, Eugster WJ. Sustainability aspects of geothermal heat pumps. In: 27th workshop on geothermal reservoir engineering, Stanford University. California; January 28–30, 2002, SGP-TR-171. p. 1–6.
5. Rybach L, Megel T, Eugster WJ. At what time scale are geothermal resources renewable? In: world geothermal congress 2000, Kyushu – Tohoku, Japan; May 28–June 10 2000.