1. On the economy of the heating or cooling of buildings by means of air;Thomson;Glasgow Philosophical Society Proceedings,1852
2. IEA Heat Pump Centre. Peter Ritter von Rittinger International Heat Pump Award. Available from: 〈http://www.heatpumpcentre.org/en/hppactivities/rittingeraward/Sidor/default.aspx〉.
3. Zoelly H. Heizverfahren. Patent CH59350; 1912.
4. The Heat Pump. Available from: 〈http://what-when-how.com/inventions/heatpumpinventions/〉 [accessed 29.06.11].
5. A review of heat pump water heating systems;Hepbasli;Renewable and Sustainable Energy Reviews,2009