Columbia subject headings:
Harvard subject headings:
Air--Pollution--Government policy--Europe.
Greenhouse gases--Environmental aspects--Europe.
Synthetic fuels industry--Europe.
Synthetic fuels--Europe.
Princeton subject headings:
Automobiles--Motors--Exhaust gas--Environmental aspects.
Diesel motor--Alternative fuels.
Motor fuels--Environmental aspects.
Spark ignition engines--Alternate fuels.
Transportation--Automotive--Environmental aspects.