Aldo Leopold (2013). “Aldo Leopold: A Sand County Almanac & Other Writings on Conservation and Ecology: (Library of America #238)”, p.223, Library of America
Aldo Leopold (2013). “Aldo Leopold: A Sand County Almanac & Other Writings on Conservation and Ecology: (Library of America #238)”, p.104, Library of America
Aldo Leopold (2013). “Aldo Leopold: A Sand County Almanac & Other Writings on Conservation and Ecology: (Library of America #238)”, p.164, Library of America