Columbia subject headings:
Harvard subject headings:
Boundaries--International cooperation--History--21st century--Sources.
Council of Europe--History--21st century--Sources.
Europe--Politics and government--21st century--Sources.
Interregionalism--Europe--History--21st century--Sources.
Regionalism--Europe--International cooperation--History--21st century--Sources.
Princeton subject headings:
European Union countries--Boundaries.
European cooperation.
Regional planning--European Union countries.
Regionalism--Europe.