Columbia subject headings:
Organization of Petroleum Exporting Countries.
Petroleum industry and trade--Persian Gulf Region.
Petroleum industry and trade.
Petroleum reserves.
Harvard subject headings:
Organization of Petroleum Exporting Countries.
Petroleum industry and trade--Persian Gulf Region
Petroleum industry and trade.
Petroleum reserves.
Princeton subject headings:
Organization of Petroleum Exporting Countries.
Petroleum industry and trade--Persian Gulf Region.
Petroleum industry and trade.
Petroleum reserves.