Columbia subject headings:
Christianity and other religions--Islam--History.
Islam--Relations--Christianity--History.
Harvard subject headings:
Catholic Church--Foreign relations--Turkey.
Catholic Church--Relations--Islam.
Christianity and other religions--Islam
George, of Trebizond, 1396-1486
Islam--Relations--Catholic Church
Islam--Relations--Christianity
Nicholas, of Cusa, Cardinal, 1401-1464
Turkey--Foreign relations--Catholic Church.
Turkey--History--1453-1683.
Princeton subject headings: