• http://climatecolab.org/
• http://www.asle.org/
• http://hfe-observatories.org/
• http://www.un.org/sustainabledevelopment/
• http://www.footprintnetwork.org/en/index.php/GFN/page/calculators/
• http://www.stonybrook.edu/commcms/humanities/events/hfe.html