1. “A comparison of geothermal with oil and gas well drilling costs”;Augustine,2006
2. “A dynamic function for energy return on investment”;Dale;Sustainability,2011
3. “Peak phosphorus”;Patrick;Energy Bulletin,2007
4. “The Energy Return of (Industrial) Solar—Passive Solar, pv, Wind and Hydro”;Hall;Appendix G-2: Photovoltaics, The Oil Drum,2008