Columbia subject headings:
Harvard subject headings:
Crusades--Sources
History--Study and teaching--France.
History--Study and teaching--Germany
Textbooks--France--History.
Textbooks--Germany--History.
Princeton subject headings:
Crusades--Sources.
History--Study and teaching--France.
History--Study and teaching--Germany.
Textbooks--France--History.
Textbooks--Germany--History.