1. Boyle, G.: Renewable energy - 2nd ed., Oxford University Press, Oxford, 2004
2. Sorensen, B.: Renewable energy: its physics, engineering, use, environmental impacts, economy and planning aspects - 3rd ed., Elsevier/Academic Press, Burlington, 2004
Rules EN 255-1, 255-2, 255-3 Air condition, liquid chilling packages and heat pump with electrically driven compressors – Heating mode – Part 3:Testing and requirements for marking for sanitary hot water units. Energy for future: Renewable sources of Energy-White paper for a Common Strategy and Action Plan, Rules EN 12975 -Solar collectors and construction elements. Works plan of European heating products for heat pump etc.