Columbia subject headings:
Harvard subject headings:
Gregorovius, Ferdinand, 1821-1891--Congresses.
Historiography--Congresses
History--Philosophy--Congresses
History--Study and teaching--Congresses
Princeton subject headings:
Gregorovius, Ferdinand, 1821-1891--Congresses.
Historiography--Congresses.
History--Philosophy--Congresses.
History--Study and teaching--Congresses.