Columbia subject headings:
Harvard subject headings:
Alternative fuel vehicles--Research--United States.
Automobiles--Fuel systems--Research--United States.
Fuel cells--Research--United States.
Hydrogen cars--Research--United States.
Princeton subject headings:
Alternative fuel vehicles--Research--United States.
Automobiles--Fuel systems--Research--United States.
Fuel cells--Research--United States.
Hydrogen cars--Research--United States.