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 | O'Connor, D. J. Aquinas and Natural Law . London: Macmillan, 1967.
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 | Ogilvie, R. M. The Romans and Their Gods . London, 1969.
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 | Ostwald, Martin. From Popular Sovereignty to the Sovereignty of Law: Law, Society, and Politics in Fifth-Century Athens . Berkeley: University of California Press, 1986.
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 | Painter, Sidney. Feudalism and Liberty . Edited by Fred A. Cazel, Jr. Baltimore: Johns Hopkins Press, 1961.
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 | Pallister, Anne. Magna Carta: The Heritage of Liberty . Oxford: Clarendon Press, 1971.
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 | Parker, Henry. Animadversions Animadverted . 1642.
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 | . Contra Replicant . 1643.
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 | Patterson, Bennett. B. The Forgotten Ninth Amendment . Indianapolis: Bobbs-Merrill, 1955.
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 | Peterson, Merrill D., ed. The Portable Thomas Jefferson . New York: Viking Press, 1975.
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 | Petit, Paul. Pax Romana . Translated by James Willis. Berkeley: University of California Press, 1976.
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 | Plato. Laws .
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 | . Republic .
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