Columbia subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500.
Catholic Church--Liturgy--Texts--History and criticism.
Crusades.
War--Religious aspects--Catholic Church--History of doctrines.
Harvard subject headings:
Catholic Church--Liturgy--History of doctrines--Middle Ages, 600-1500.
Catholic Church--Liturgy--Texts--History and criticism.
Crusades
War--Religious aspects--Catholic Church--History of doctrines.
Princeton subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500.
Catholic Church--Liturgy--Texts--History and criticism.
Crusades.
War--Religious aspects--Catholic Church--History of doctrines.