Columbia subject headings:
Avars--History--Congresses.
Huns--History--Congresses.
Magyars--History--Congresses.
Harvard subject headings:
Avars--History--Congresses.
Huns--History--Congresses.
Magyars--History--Congresses.
Princeton subject headings:
Europe, Central--Civilization--Congresses.
Europe, Eastern--Civilization--Congresses.
Europe--Civilization--Slavic influences--Congresses.