These are still very weak sources. Apart from the piece by Lloyd, which appears to be an undergraduate project as discussed above, what you've added is the abstract of a non-peer-reviewed paper presented at the annual meeting of an association, and a lecture handout that appears to have been put online by its author. None of your three sources support the sentence "The Roman constitution had three main powers..."; as I've already discussed above, Lloyd describes Polybius as seeing the Roman constitution this way, not Montesquieu. So I'm going to remove this sentence, again.

The rest of your additions can remain, I think, and I will also format the references you added.  (talk)