Mary Schmich (2012). “The Best of Mary Schmich: Selected Writings by the Chicago Tribune's Winner of the 2012 Pulitzer Prize for Commentary”, p.32, Agate Digital
M. Scott Peck (2002). “The Road Less Traveled, 25th Anniversary Edition: A New Psychology of Love, Traditional Values, and Spiritual Growth”, p.15, Simon and Schuster
"We'll Never Conquer Space". Essay by Arthur C. Clarke first published in "Science Digest" (June 1960); later published in Arthur C. Clarke "Profiles of the Future: An Inquiry into the Limits of the Possible", 1962, in Arthur C. Clarke "Voices from the Sky", 1965, and in Arthur C. Clarke "Greetings, Carbon-Based Bipeds!: Collected Essays, 1934-1998", 1999.