Columbia subject headings:
Electric utilities--Law and legislation--North America.
Electric utilities--North America.
Natural gas--Law and legislation--North America.
Harvard subject headings:
Electric utilities--Law and legislation--North America.
Electric utilities--North America.
Natural gas--Law and legislation--North America.
Natural gas--North America.
Princeton subject headings:
Electric utilities--Law and legislation--North America.
Electric utilities--North America.
Natural gas--Law and legislation--North America.
Natural gas--North America.