publishing articles for users but not letting them edit it

I am using WordPress to publish a formal magazine, i.e. a magazine where I (the WordPress administrator) am also the Editor and Publisher. People submit articles to me, I attempt to fact-check them and make other edits, and then I publish them.

I would like to make each contributor’s WordPress account the “author” of the article, i.e. giving them the equivalent of “by John Smith”. However, I do not want them to be able to edit the pieces after I publish them, since pieces are already finalized and allowing an author to edit a published piece (without going through me and issuing a correction) would open the potential for abuse.

In sum, I want to assign pieces to authors without letting them edit the pieces.

What is the best way to accomplish this?