Columbia subject headings:
Harvard subject headings:
Air quality management--Europe.
Automobiles--Europe--Motors--Exhaust gas.
Automobiles--Motors--Exhaust gas--Europe.
Scrap metal industry--Europe.
Princeton subject headings:
Automobiles--Motors--Exhaust gas--Environmental aspects--Europe.
Automobiles--Motors--Exhaust gas--Environmental aspects.
Automobiles--Scrapping--Europe.
Automobiles--Scrapping.