United Nation Environment Program (UNEP) (2013) Resource Efficiency and Sustainable Consumption and Production. Negative Economic Impacts of Tourism. http://www.unep.org/resourceefficiency/ Business/SectoralActivities/Tourism/FactsandFguresaboutTourism/ImpactsofTourism/EconomicImpact sofTourism/NegativeEconomicmpactsofTourism/tabid/78784/Default.aspx
 Sanchez-Azofeifa, G., Daily, C.G., Pfaff, A. and Busch, C. (2003) Integrity and Isolation of Costa Rica’s National Parks and Biological Reserves: Examining the Dynamics of Land-Cover Change. Biological Conservation, 109, 123-135.
 Patterson, J., Linden, E., Edward, P., Wilhelmsson, D. and Lofgren, I. (2009) Community-Based Environmental Education in Fishing Villages of Tuticorin and Its Role in Conservation of the Environment. Australian Journal of Adult Learning, 49, 383-393.
 Juttner, F., Backhaus, D., Mattias, U., Essers, U., Greiner, R. and Mahr, B. (1995) Emissions of Tow- and Four-Stroke Outboard Engines Engines—II. Impact on Water Quality. Water Research, 29, 1983-1987.
 Juttner, F., Backhaus, D., Mattias, U., Essers, U., Greiner, R. and Mahr, B. (1995) Emissions of Two and Four-Stoke Outboard Engines—I. Quantification of Gases and VOC. Water Research, 29, 1976-1982.
 Codarin, A., Wysocki, L., Ladich, F. and Picciulin, M. (2009) Effects of Ambient and Boat Noise on Hearing and Communication in Three Fish Species Living in a Marine Protected Area (Miramare, Italy). Marine Pollution Bulletin, 58, 1880-1887.