Columbia subject headings:
Harvard subject headings:
Europe--Economic conditions.
Europe--Foreign relations.
Hubbert peak theory--Europe--History.
Natural gas--Europe--History.
Petroleum industry and trade--Europe--History.
Petroleum reserves--Europe--History.
Princeton subject headings:
Europe--Economic conditions.
Europe--Foreign relations.
Hubbert peak theory--Europe--History.
Natural gas--Europe--History.
Petroleum industry and trade--Europe--History.
Petroleum reserves--Europe--History.