Columbia subject headings:
Harvard subject headings:
Holy Roman Empire--History--Frederick II, 1215-1250.
Knights and knighthood--Holy Roman Empire--Biography.
Salza, Hermann von, -1239.
Teutonic Knights--Biography.
Princeton subject headings:
Holy Roman Empire--History--Frederick II, 1215-1250.
Knights and knighthood--Holy Roman Empire--Biography.
Salza, Hermann von, -1239.
Teutonic Knights--Biography.