if someone contribute article on our website,
1) how to confirm its unique? please give an authentic plag check links
2) what if he copied the content from expired domain, ( the one that is expired, but not deleted )
3) just to check i copied an article from an expired domain, and using few free plag checker, out of 3 copied articles, two were shown as unique,
4) even if i got cheated and i posted the article, ( because it appears to be unique ) will i be penalized by google? and if not, how much time does it take for an expired domain to be deleted completely and their articles to be as safe as genuine article.