Columbia subject headings:
Automobiles--United States--Fuel consumption.
Automobiles--United States--Pollution control devices.
Transportation--Energy conservation--United States.
Transportation--United States--Energy conservation.
Harvard subject headings:
Automobiles--United States--Fuel consumption
Automobiles--United States--Pollution control devices.
Transportation--Energy conservation--United States.
Princeton subject headings:
Automobiles--United States--Fuel consumption.
Automobiles--United States--Pollution control devices.
Transportation--Energy conservation--United States.