1. Carnegie Council on Adolescent Development. The Turning Point. New York: Carnegie Corporation.
2. 1908. Book VI, “The Winter Walk at Noon.” In The Poetical Works of William Cowper, ed. 267, lines 88-98. London: Macmillan.
3. 1990. The World of Systems: A New Elective for 7th and 8th Grade Students at Orange Grove Middle School, Tucson, AZ 85718, U.S.A.
4. Learner-directed systems education: A successful example