Columbia subject headings:
Harvard subject headings:
Altars.
Catholic Church--Liturgy--History.
Church history--Middle Ages, 600-1500
Liturgics--History--Middle Ages, 600-1500.
Princeton subject headings:
Altars.
Catholic Church--Liturgy--History.
Church history--Middle Ages, 600-1500.
Liturgics--History--Middle Ages, 600-1500.