1. Dr. Alvin, Virginia, and Robert Silverstein, The Respiratory System, (New York: Henry Holt & Co., 1994) 41
2. Peter C. Gega, Science in Elementary Education, (New York: Macmillan Pub., 1986) 434 – 435
3. Thomas Kardos, 75 Easy life Science Demonstration, (Portland, Maine: J. Weston Walch, Pub., 1996) 6
4. Kardos, 15
5. Gega, 510
6. Paul R. Ehrlich, The Machinery of Nature, (New York: Simon and Schuster, 1986) 24
7. William J. Jacobson and Abby Farry Bergman, Science for Children, (Englewood Cliffs, New Jersey: Prentice Hall, Inc. 1987) 307
8. Ehrlich, 36-38
9. Kardos, 16
10. Kardos, 12
11. Kardos, 11
12. Kardos, 4
13. Donald M. Silver, Life On Earth: Biology Today, (New York, Random House, 1983) 13-15
14. Gega, 402
15. Gega, 402
16. Gega, 402
17. Gega, 507
18. Kardos, 20
19. Suzuki, David, Looking at the Environment, (New York: John Wiley and Sons, 1991) 30-31
20. Suzuki, 33