Columbia subject headings:
Air quality management--England--London.
Air quality management--Mexico--Mexico City.
Harvard subject headings:
Air quality management--England--London.
Air quality management--Mexico--Mexico City.
Air quality--Government policy--England--London.
Air quality--Government policy--Mexico--Mexico City.
Princeton subject headings:
Air quality management--England--London.
Air quality management--Mexico--Mexico City.
Air quality--Government policy--England--London.
Air quality--Government policy--Mexico--Mexico City.