Columbia subject headings:
Gas industry--Government policy--United States.
Gas industry--United States.
Natural gas--Prices--United States.
Harvard subject headings:
Gas industry--Government policy--United States
Gas industry--United States
Natural gas--Prices--United States
Natural gas--United States--Price policy.
Princeton subject headings:
Gas industry--Government policy--United States.
Gas industry--United States.
Natural gas--Prices--United States.
Natural gas--United States--Prices.