Collins, Billy. “Marginalia.” Picnic, Lightning. Pittsburgh: University of Pittsburgh Press, 1998.†
“Denise Levertov.” Cengage Learning. http://college.cengage.com/english/heath/syllabuild/iguide/levertov.html.††
Gore, Al. Earth in the Balance: Ecology and the Human Spirit. New York: Penguin Group, 1992.†††
Levertov, Denise. “Variation on a Theme by Rilke.” Breathing the Water. New York: New Directions Publishing Corporation, 1987.
Thoreau, Henry David. Walden. New York: C. E. Merrill Co.,1910.
Wordsworth, William. “The World Is Too Much with Us.” The Complete Poetical Works. London: Macmillan and Co., 1888.
†“Marginalia” from Picnic, Lightning, by Billy Collins, ©, 1998. All rights are controlled by the University of Pittsburgh Press, Pittsburgh, PA 15260. Used by permission of the University of Pittsburgh Press
††“Variation on a Theme by Rilke (The Book of Hours, Book I, Poem 1, Stanza 1) by Denise Levertov, from Breathing the Water, copyright © 1987 by Denise Levertov. Reprinted by permission of New Directions Publishing Corp.
††Excerpts from EARTH IN THE BALANCE: Ecology and the Human Spirit by Al Gore. Copyright © 1992 by Senator Al Gore. Used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.