4Bangsund, D A, F L Leistritz and J A Leitch. Assessing Economic Impacts of Biological Control of Weeds: The Case of Leafy Spurge in the Northern Great Plains of the United States[J]. Journal of Environmental Management, 1999 (56): 35-43.
5Crosby, A W. Ecological Imperialism: The Biological Expansion of Europe[M]. Cambridge University Press. New York.1986. 900 - 936.
6Daszak, P A, A Cunningham, and A D Hyatt. Emerging Infectious Diseases of Wildlife: Threats to Biodiversity and Human Health[J]. Science, 2000(287) :443 - 449.