"Pentarchy". Encyclopædia Britannica. Retrieved February 14, 2010. "The proposed government of universal Christendom by five patriarchal sees under the auspices of a single universal empire. Formulated in the legislation of the emperor Justinian I (527–65), especially in his Novella 131, the theory received formal ecclesiastical sanction at the Council in Trullo (692), which ranked the five sees as Rome, Constantinople, Alexandria, Antioch, and Jerusalem".
