Renaissance authors who spoke highly of republics were rarely critical of monarchies. While Niccolò Machiavelli's "Discourses on Livy" is the period's key work on republics, he also wrote the treatise "The Prince," which is better remembered and more widely read, on how best to run a monarchy. The early modern writers did not see the republican model as universally applicable; most thought that it could be successful only in very small and highly urbanized city-states. Jean Bodin in "Six Books of the Commonwealth" (1576) identified monarchy with republic.