Percy Bysshe Shelley (1842). “The masque of Anarchy, a poem, with a preface by L. Hunt. To which is added, Queen Liberty; Song- To the men of England”, p.18
Alan Greenspan's Testimony Before the Committee on Banking and Financial Services, U.S. House of Representatives, www.federalreserve.gov. July 24, 1998.
Aldo Leopold (2013). “Aldo Leopold: A Sand County Almanac & Other Writings on Conservation and Ecology: (Library of America #238)”, p.104, Library of America