Columbia subject headings:
Europe--Politics and government--21st century.
Great powers--History--21st century.
World politics.
Harvard subject headings:
European Union countries--Foreign relations--21st century
European Union countries--Politics and government--21st century.
World politics--21st century
Princeton subject headings:
Diplomacy.
Europe--Politics and government--21st century.
Great powers--History--21st century.
World politics.