Columbia subject headings:
Harvard subject headings:
Biodiesel fuels--Law and legislation--United States.
Diesel motor--Alternative fuels--Research--United States.
Diesel motor--United States--Alternate fuels--Research--United States.
Energy policy--United States
Methane industry--Law and legislation--United States.
Motor vehicle fleets--Government policy--United States.
Natural gas--Hydrates--Research--United States.
Natural gas--United States--Hydrates.
Princeton subject headings:
Biodiesel fuels--Law and legislation--United States.
Diesel motor--Alternative fuels--Research--United States.
Energy policy--United States.
Methane industry--Law and legislation--United States.
Motor vehicle fleets--Government policy--United States.
Natural gas--Hydrates--Research--United States.