Aldo Leopold (2013). “Aldo Leopold: A Sand County Almanac & Other Writings on Conservation and Ecology: (Library of America #238)”, p.209, Library of America
John Newton (1782). “An Authentic Narrative of Some Remarkable and Interesting Particulars in the Life of ********.: Communicated in a Series of Letters, to the Reverend Mr. Haweis, ... and by Him (at the Request of Friends) Now Made Public”, p.19