Columbia subject headings:
Crusades.
Europe--Religious life and customs.
Liturgics--Europe--History--To 1500.
Harvard subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500.
Catholic Church--Liturgy--Texts--History and criticism.
Crusades
Europe--Religious life and customs.
Liturgics--Europe--History--To 1500.
Princeton subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500.
Catholic Church--Liturgy--Texts--History and criticism.
Crusades.
Europe--Religious life and customs.