Мных, А. С., Н. А. Баташова, С. А. Левченко, and Д. Е. Ерохин. “The Analyses of Heating System Economic Efficiency With Additional Energy Source”. Eastern-European Journal of Enterprise Technologies, vol. 6, no. 7(48), Nov. 2010, pp. 4-6, doi:10.15587/1729-4061.2010.3354.