Columbia subject headings:
Church and state--Holy Roman Empire--History.
Church history--Middle Ages, 600-1500.
Church--History of doctrines--Middle Ages, 600-1500.
Leo IX, Pope, 1002-1054.
Harvard subject headings:
Princeton subject headings:
Church and state--Holy Roman Empire--History.
Church history--Middle Ages, 600-1500.
Church--History of doctrines--Middle Ages, 600-1500.
Leo IX, Pope, 1002-1054.