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Cita Chicago (17th ed.)organization of the petroleum exporting countries. Annual Report 2017. austria: grasl druck & neue medien gmbh, 2017.
Cita MLA (9th ed.)organization of the petroleum exporting countries. Annual Report 2017. grasl druck & neue medien gmbh, 2017.
Atenció: Aquestes cites poden no estar 100% correctes.