Plagiarism control

Hello,

I would like to ask you for advice how to control that publisched post is not a copy. I would like to control the post in status "pending" to have possibility to delete copyed posts before is publish.

I have tryed:
- Wordpress Copyscape Plugin
- WP Pirates Search

Both of this dont work right for me. I am using WPMU 3.1.3

Have you any Idea if there is plugin for this, even paid?
I found article on wiki http://en.wikipedia.org/wiki/Plagiarism_detection, have you experience with some of these tools used with wordpress?

Do you use another tools?

Thanks,

Bigdrobek