OGRADY, Sean P. "Pilgrims to the Wild." DAI 52 (March 1992): 3285-A .
OMALLEY, Therese. "Appropriation and Adaptation: Early Gardening Literature in America." Huntington Library Quarterly 55 (1992).
ODUM, Eugene Pleasants, 1913-, Ecology: a Bridge between Science and Society , Sunderland, Mass : Sinauer Associates, 1996.
OELSCHLAEGER, Max. After Earth Day: Continuing the Conservation Effort. Denton: U of North Texas P, 1992.
Caring for Creation: An Ecumenical Approach to the Environmental Crisis. New Haven: Yale UP, l994.
The Idea of Wilderness: From Prehistory to the Age of Ecology. New Haven: Yale UP, 1991.
The Wilderness Condition: Essays on Environment and Civilization. San Francisco: Sierra Club Books, 1992.
O'LOUGHTIN, Carleen, Economic and Political Change in the Leeward and Windward Islnads, N. Haven, 1968.
OLSEN, Brett J. "Wallace Stegner and the Environmental Ethic: Environmentalism as a Rejection of Western Myth." Western American Literature 29.2 (1994): 123-42.
ONG, Walter S. "Personalism and the Wilderness." Kenyon Review 21(1959): 297-304.
OPIE, John, ed. Americans and Environment: The Controversy Over Ecology. Lexington, MA: D.C. Heath, 1971.
The Law of the Land: Two Hundred Years of American Farm Land Policy. Lincoln and London: University of NebraskaPress, 1987.
ORR, David W. Ecological Literacy: Education and the Transition to a Postmodern World. Albany: State U of New York P, l992.
ORTIZ, Simon J. After and Before the Lightening. Tucson: U of Arizona P, 1994. .
ORTIZ MONASTERIO, Fernando, Tierra Profanada: Historia Ambiental de Mexico, Mexico, DF., Instituto Nacional de Antropologia e Historia, 1987.
OZA, G.M. , "An Indian View of Man and Nature", Environ. Conservation, 10(4), 1983: 331-335.
OSBORNE, Michael, Nature, the Exotic and the Science of French Colonialism, Bloomington, 1994
OWINGS, Coren C., Environmental Values 1860-1972. A Guide to Information Sources, Michigan, 1976.
OWENS, Louis. "The American Indian Wilderness." American Nature Writing Newletter 6.2 (1994): 7-8. .