Columbia subject headings:
Air--Pollution--California.
Air--Pollution--United States.
Automobiles--Motors--Exhaust gas.
Environmental policy--California.
Environmental policy--United States.
Harvard subject headings:
Air quality management--California
Air--Pollution--California
Air--Pollution--United States
Automobiles--Motors--Exhaust gas
Environmental policy--California
Environmental policy--United States
Princeton subject headings:
Air--Pollution--California.
Air--Pollution--United States.
Automobiles--Motors--Exhaust gas.
Environmental policy--California.
Environmental policy--United States.