JOTANOVIĆ, Milovan, TADIĆ, G., KROPE, Jurij and GORIČANEC, Darko, 2012, Analysis of two-stage high- temperature heat pump efficiency. International journal of systems applications, engineering & development [online]. 2012. Vol. 6, no. 5, p. 350–363. [Accessed 14 March 2025]. Retrieved from: http://www.naun.org/multimedia/UPress/saed/16-564.pdf