Agrusa, J. and Guidry, J. (1999). Ecotourism and Sustainable Development of the Maya Rain Forest in Central America / First Pan-American Conference Proceedings.
Boo, E. (1990). Ecotourism: The Potentials and Pitfalls. World Wildlife Fund: Washington, D.C. Cater, E. (1993). Ecotourism in the Third World: Problems for Sustainable Tourism Development. Tourism Management, pp. 14, 2, 107-115.
Himberg, N. (2006). Community-based Ecotourism as a Sustainable Development Option in the Taita Hills, Kenya. Master ́ s thesis. University of Helsinki Inskeep,
E. (1991). Tourism Planning: An Integrated and Sustainable Development Approach. Van Nostrand Reinhold: New York.
Lamba, B. (1987). Status survey report of fauna. Nanda Devi National Park. Records of the Zoological survey of India. Occasional Paper No. 103. pp. 50.
Lavkumar, K. (1977). Report on the preliminary survey of the Nanda Devi basin. WWF-India, Bombay. pp. 27.
Mogal, Z and Agrusa, J. (1997). The Potential to Develop the State of Mississippi into an Ecotourism Destination. Published proceedings "Graduate Education and Graduate Students Research in Hospitality and Tourism," pp.189-198.
Sherman, P.B and Dizon, J.A. (1991). "Nature Tourism: Determining if it pays." In T. Wheland (ed.), Ecotourism. Covelo, CA: Island Press.
Srivastava, S. (1999). Management plan for the valley of flowers national park. Wildlife Preservation Organization, Uttar Pradesh. UNEP-World Conservation Monitoring Center (2005). Under World Heritage sites Nanda Devi and Valley of flowers national Parks, Uttaranchal India.
Ziegler, C.G. ; Lamatsch, D.K. ; Steinlein, C. ; Engel, W. ; Schartl, M. and Schmid, M. (2003) The giant B chromosome of the cyprinid fish Alburnus alburnus harbours a retrotransposon-derived repetitive DNA sequence. Chromosome Res. 11: 23-35.