1. National Geographic (no date). Center for Sustainable Destinations. About Geotourism. Retrieved March 27, 2006, from http://www.nationalgeographic.com/travel/sustainable/about_geotourism.html
2. Stueve, A. M., Cook, S. D., & Drew, D. (2002). The geotourism study: Phase 1 executive summary. Washington, DC: Travel Industry Association of America, National Geographic Traveler.