Lund, J. W., Freeston, D. H., & Boyd, T. L. (2005). Direct application of geothermal energy: 2005 Worldwide review. Geothermics, 34, 691-727. http://dx.doi.org/ 19 Şubat 2011 tarihinde Wayback Machine sitesinde arşivlendi. doi:10.1016/j.geothermics.2005.09.003
Lund, J. W., Freeston, D. H., & Boyd, T. L. (2005). Direct application of geothermal energy: 2005 Worldwide review. Geothermics, 34, 691-727. http://dx.doi.org/ 19 Şubat 2011 tarihinde Wayback Machine sitesinde arşivlendi. doi:10.1016/j.geothermics.2005.09.003