Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsTornado Activity in the U.S. 1950-2007http://demonstrations.wolfram.com/TornadoActivityInTheUS19502007/]]>http://demonstrations.wolfram.com/TornadoActivityInTheUS19502007/