Students should be rewarded for checking sources, and (moderately?) penalized for not doing so. I would say that at a minimum, every fictitious source knocks of

Students should be rewarded for checking sources, and (moderately?) penalized for not doing so. I would say that at a minimum, every fictitious source knocks off a full letter grade. And make sure students know this. They will adapt. And it might get them to the sources, at least superficially (yeay?) to check for existence/non-existence.