- Francke, Chip. Personal interview. 5 Oct. 2009.
- http://greennature.com/article231.html N.p., 2009. Web. 18 Oct. 2009.
- Johnson, and Raven. Holt Biology. N.p.: Holt, Rinehart and Winston, 2005. Print.
- Francke, Chip. Personal interview. 5 Oct. 2009.
- http://greennature.com/article231.html N.p., 2009. Web. 18 Oct. 2009.
- Johnson, and Raven. Holt Biology. N.p.: Holt, Rinehart and Winston, 2005. Print.
