1. Man and Landscape Change in the Banff National Park Area Before 1911;Byrne,1968
2. Some Comments on National Parks and Surrounding Human Populations in Africa;Curry-Lindahl,1972
3. Ecological Impact of Recreation and Tourism Upon Temperate Environments;International Union for the Conservation of Nature,1967
4. The Development of the Tourist Travel System;Lundgren;The Tourist Review,1973