Columbia subject headings:
Harvard subject headings:
Balkan Peninsula--Foreign relations.
Balkan Peninsula--History--Congresses.
Balkan Peninsula--History.
Balkan Peninsula--Politics and government--Congresses.
Balkan Peninsula--Politics and government.
Europe, Central--History.
Europe, Eastern--History.
Power (Social sciences)--Balkan Peninsula--History.
Princeton subject headings:
Balkan Peninsula--History--Congresses.
Balkan Peninsula--Politics and government--Congresses.