Columbia subject headings:
Natural gas--Government policy--United States--Congresses.
Natural gas--Law and legislation--United States--Congresses.
Harvard subject headings:
Natural gas--Government policy--United States--Congresses.
Natural gas--Law and legislation--United States--Congresses.
Princeton subject headings:
Natural gas--Government policy--United States--Congresses.
Natural gas--Law and legislation--United States--Congresses.