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Petroleum industry and trade 382 Gas industry 50 Political aspects 42 History 40 Environmental aspects 39 Economic aspects 26 Government policy 24 Petroleum 21 Energy policy 20 Social aspects 18 Economic conditions 17 Politics and government 17 Prices 17 Petroleum reserves 15 Foreign relations 14 Petroleum law and legislation 14 Petroleum products 14 Management 13 Energy industries 12 Law and legislation 12 Natural gas 12 Petroleum engineering 10 Power resources 10 Foreign economic relations 9 Energy consumption 8 Finance 8 Social conditions 8 Social responsibility of business 7 Data processing 6 Economic development 6