Columbia subject headings:
Harvard subject headings:
Agricultural pollution--European Union countries.
Nitrates--Environmental aspects--European Union countries.
Nonpoint source pollution--Government policy--European Union countries.
Water--Pollution--Law and legislation--European Union countries.
Princeton subject headings:
Agricultural pollution--European Union countries.
Nitrates--Environmental aspects--European Union countries.
Nonpoint source pollution--Government policy--European Union countries.
Water--Pollution--European Union countries.