Columbia subject headings:
Harvard subject headings:
Crusades--Later, 13th, 14th, and 15th centuries--Sources.
Hungary--History--1000-1699--Sources.
Turkey--History--Murat II, 1421-1451--Sources.
Princeton subject headings:
Crusades--13th-15th centuries--Sources.
Hungary--History--1000-1699--Sources.
Turkey--History--Murad II, 1421-1451--Sources.