Columbia subject headings:
Byzantine Empire--History--Constantine XI Dragases, 1448-1453.
Byzantine Empire--History--John VIII Palaeologus, 1425-1448.
Harvard subject headings:
Byzantine Empire--History--1081-1453--Sources.
Istanbul (Turkey)--History--Siege, 1453--Sources.
Princeton subject headings:
Byzantine Empire--History--1081-1453--Sources.
Istanbul (Turkey)--History--Siege, 1453--Sources.