（48）George Perkins Marsh, Man and Nature, p. 36.
    （49）John Warfield Simpson, Visions of Paradise: Glimpses of Our Landscape‘s Legacy, Berkeley and Los Angeles: University of California Press, 1999, p. 150.
    （50）Robert L. Dorman, A Word for Nature: Four Pioneering Environmental Advocates, 1845-1913, Chapel Hill: University of North Carolina, 1998, p. 44.
    （51）Robert Gottlieb, Forcing the Spring: The Transformation of the American Environmental Movement, Washington D. C.: Island Press, 2005, p. 56.
    （52）Robert L Dorman, A Word for Nature: Four Pioneering Environmental Advocates, 1845-1913, p. 105.
    （53）[日]岸根卓郎著，何鉴译：《环境论：人类最终的选择》，南京大学出版社1999年版，第1-6页。