1. Respect for the environment as a basic condition for the tourist business in the future: A tour operator's review;Amrhein,1993
2. A window to the natural world: The design of ecotourism facilities;Andersen,1993
3. Unrealized tourism potential: the case of sub-Saharan Africa;Ankomah;Tourism Management,1990
4. Trends and problems in eco-tourism;Ashton,1991
5. Can places be sold for tourism?;Ashworth,1990