Organization of Petroleum Exporting Countries. OPEC bulletin. Organization of the Petroleum Exporting Countries.
Citazione stile Chigago Style (17a edizione)Organization of Petroleum Exporting Countries. OPEC Bulletin. Vienna: Organization of the Petroleum Exporting Countries.
Citatione MLA (9a ed.)Organization of Petroleum Exporting Countries. OPEC Bulletin. Organization of the Petroleum Exporting Countries.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.