Columbia subject headings:
Air quality management--International cooperation.
Air--Pollution--Law and legislation--Europe.
Transboundary pollution--Law and legislation--Europe.
Harvard subject headings:
Air quality management--International cooperation
Air--Pollution--Law and legislation--Europe.
Transboundary pollution--Law and legislation--Europe.
Princeton subject headings:
Air quality management--International cooperation.
Air--Pollution--Law and legislation--Europe.
Transboundary pollution--Law and legislation--Europe.