Columbia subject headings:
Harvard subject headings:
Church history--Middle Ages, 600-1500--Sources.
Council of Aachen (809)
Councils and synods--Europe--History--Sources.
Europe--Church history--600-1500--Sources.
Holy Spirit--Procession--Early works to 1800.
Holy Spirit--Procession--History of doctrines--Middle Ages, 600-1500.
Trinity--Early works to 1800.
Trinity--History of doctrines--Middle Ages, 600-1500.
Princeton subject headings:
Carolingians--Sources.
Church history--Middle Ages, 600-1500--Sources.
Council of Aachen (809)
Councils and synods--Europe--History--Sources.
Europe--Church history--Sources.