Columbia subject headings:
International economic relations.
Organization of Petroleum Exporting Countries.
Petroleum industry and trade--United States.
Petroleum industry and trade.
Harvard subject headings:
International economic relations.
Organization of Petroleum Exporting Countries.
Petroleum industry and trade--United States
Petroleum industry and trade.
Princeton subject headings:
International economic relations.
Organization of Petroleum Exporting Countries.
Petroleum industry and trade--United States.
Petroleum industry and trade.