Proof, as in 100% proof ? Or prove ? And Plagiarized.<p>You are going to have to prove 'provenance'.<p><a href="http://en.wikipedia.org/wiki/Provenance" rel="nofollow">http://en.wikipedia.org/wiki/Provenance</a><p>This is a very complicated subject, the best thing you can do is to document very carefully the process of creation, time stamps and so on, and then to use those to challenge the people that cloned your content.<p>Mostly in the context of college, but useful stuff anyway:<p><a href="http://www.bobbyelliott.com/Plagiarism.htm" rel="nofollow">http://www.bobbyelliott.com/Plagiarism.htm</a>