4Leslie Paul Thiele. Environmentalism for a New Millennium, Oxford University Press,1999., ppxⅷ.
5Kristin Shrader Frechett. Practical Ecology and Foundation for Environmental Ethics, The Journal of Philosophy, Vol XCⅡ,No. 12, December 1995,pp622.
6Leslie Paul Thiele: Environmentalism for a New Millennium, Oxford University Press,1999., pp39.
7Ramachandra Guha: Radical American Environmentalism and Wilderness Preservation: A Third World Critique, Pierce/van Dever 2nd Edition , Wadsworth Publishing Company,pp358-364.