Columbia subject headings:
Apostolic succession--History of doctrines.
Christian union.
Church polity--History--Early church, ca. 30-600.
Harvard subject headings:
Apostolic succession--History of doctrines--Early church, ca. 30-600.
Bishops--History.
Church polity and Christian union.
Church polity--History--Early church, ca. 30-600.
Church--Unity
Orthodox Eastern Church--Doctrines.
Princeton subject headings: