Columbia subject headings:
Germany--History--Frederick II, 1215-1250--Sources.
Military religious orders--Germany--Prussia--History--Sources.
Prussia (Germany)--History--Sources.
Teutonic Knights--History--Sources.
Harvard subject headings:
Germany--History--Frederick II, 1215-1250--Sources.
Military religious orders--Baltic Sea Region--History--Sources.
Military religious orders--Germany--Prussia--History--Sources.
Prussia (Germany)--History--Sources.
Teutonic Knights--History--Sources.
Princeton subject headings:
Germany--History--Frederick II, 1215-1250--Sources.
Military religious orders--Baltic Sea Region--History--Sources.
Military religious orders--Germany--Prussia--History--Sources.
Prussia (Germany)--History--Sources.
Teutonic Knights--History--Sources.