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