Papal bull
According to the "Catholic Encyclopedia", of the 81 universities established in pre-Reformation Europe, 13 were established "ex consuetudine" without any form of charter, 33 by Papal bull alone, 20 by both Papal bull and imperial or royal charter, and 15 by imperial or royal charter alone. Universities established solely by royal (as distinct from imperial) charter did not have the same international recognition – their degrees were only valid within that kingdom.