Welcome to Wikipedia. Although everyone is welcome to contribute constructively to the encyclopedia, adding content without citing a reliable source, as you did with to Coefficient of restitution, is not consistent with our policy of verifiability. Take a look at the welcome page to learn more about contributing to this encyclopedia. If you are familiar with Wikipedia:Citing sources, please take this opportunity to add references to the article. Petrb (talk) 18:00, 5 January 2011 (UTC)
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