Columbia subject headings:
Harvard subject headings:
Crusades
Crusades--First, 1096-1099
Crusades--Second, 1147-1149
Religion--History--12th century.
Violence--History--12th century.
War--History--12th century.
Princeton subject headings:
Crusades--First, 1096-1099.
Crusades--Second, 1147-1149.
Crusades.
Religion--History--12th century.
Violence--History--12th century.
War--History--12th century.