1. The Random House Dictionary of the English Language. 2nd ed. Unabridged. New York: Random House; 1987, p.1917.
2. Leopold A. A Sand Country Almanac. In: Russell R, Russell T, editors. On the loose, Washington, DC: Sierra Club Ballantine Books; 1964.
3. Silent Spring;Carson,1962
4. Death comes to the Peregrine falcon. New York Times Magazine; 1970.
5. For earth's sake: the life and times of David Brower;Brower,1990