Columbia subject headings:
Natural gas--Law and legislation--United States--States.
Oil pollution of soils--United States--States.
Petroleum law and legislation--United States--States.
Petroleum products--Pollution--United States--States.
Petroleum--Prospecting--United States--States.
Harvard subject headings:
Natural gas--Law and legislation--United States
Petroleum law and legislation--United States.
Petroleum waste--Law and legislation--United States.
Petroleum waste--Law and legislation.
Princeton subject headings: