Columbia subject headings:
Petroleum industry and trade--North America--Periodicals.
Harvard subject headings:
Energy development--North America--Periodicals.
Energy industries--North America--Periodicals.
Petroleum industry and trade--North America--Periodicals.
Princeton subject headings:
Energy development--North America--Periodicals.
Energy industries--North America--Periodicals.
Petroleum industry and trade--North America--Periodicals.