Columbia subject headings:
Petroleum industry and trade--Developing countries--Congresses.
Petroleum--Refining--Congresses.
Harvard subject headings:
Developing countries--Petroleum industry and trade--Congresses.
Petroleum industry and trade--Developing countries--Congresses.
Petroleum--Refining--Congresses
Princeton subject headings:
Petroleum industry and trade--Developing countries--Congresses.
Petroleum--Refining--Congresses.