Columbia subject headings:
Automobiles--Motors--Exhaust gas--Congresses.
Diesel motor exhaust gas--Congresses.
Polycyclic compounds--Environmental aspects--Congresses.
Harvard subject headings:
Princeton subject headings:
Automobiles--Motors--Exhaust gas--Congresses.
Diesel motor exhaust gas--Congresses.
Polycyclic compounds--Environmental aspects--Congresses.