References

Tornadoes. (n.d.). Retrieved February 1, 2010, from http://www.weather.com/‌encyclopedia/‌tornado/‌form.html

Tornado Information: Definition and Prevalence
. (n.d.). Retrieved January 21, 2010, from http:/‌www.weather.com/‌ready/‌tornado/‌index.html

12 Twisted Tornado Facts
. (2009, June 18). Retrieved January 26, 2010, from http://www.livescience.com/‌environment/‌090618-tornado-facts.html