Columbia subject headings:
Church history--Middle Ages, 600-1500.
Papacy--History.
Harvard subject headings:
Church history--Middle Ages, 600-1500
Holy Roman Empire--Church history--Congresses.
Holy Roman Empire--History--843-1273--Congresses.
Papacy--History
Princeton subject headings:
Church history--Middle Ages, 600-1500.
Papacy--History.