Columbia subject headings:
Harvard subject headings:
Balkan Peninsula--Foreign relations--European Union countries.
European Union countries--Foreign relations--Balkan Peninsula.
European Union--Balkan Peninsula.
European Union--Membership.
Princeton subject headings:
Balkan Peninsula--Foreign relations--European Union countries.
European Union countries--Foreign relations--Balkan Peninsula.
European Union--Balkan Peninsula.
European Union--Membership.