1. The EU climate and energy package. European Commission Brussels (http://ec.europa.eu/clima/documentation _en.htm).
2. Performance Analysis of Air-to-Water Heat Pump in Latvian Climate Conditions;Kazjonovs;Environmental and Climate Technologies,2014
3. Bălan M., Damian M., Jantschi L., Ion V.I., Study concerning the influence of some working conditions, on the heat pumps performances, Proceedings of the 35th International Symposium “Actual Tasks on Agricultural Engineering” Opatija, Croatia, 11-15 February 2008, p. 535-544.
4. Laue H. J., Heat pumps, In: K. Heinloth (ed), Landolt-Börnstein, Group VIII: Advanced Materials and Technologies, Vol. 3: Energy Technologies, Subvol. C: Renewable Energies, Springer Verlag, Heidelberg-Berlin, 2006.
5. Seasonal performance evaluation of electric air-to-water heat pump Systems;Dongellini;Applied Thermal Engineering,2015