Wiśniewska, Marta, and Jacek Forysiak. “Low Enthalpy Heat Sources Available for Vertical Ground Heat Exchangers. Environental and Technical Considerations”. Acta Universitatis Lodziensis. Folia Geographica Physica, no. 13, Dec. 2014, pp. 65-77, doi:10.18778/1427-9711.13.04.