Organization of Petroleum Exporting Countries. OPEC bulletin. Organization of the Petroleum Exporting Countries.
Chicago Style aipamenaOrganization of Petroleum Exporting Countries. OPEC Bulletin. Vienna: Organization of the Petroleum Exporting Countries.
MLA aipamenaOrganization of Petroleum Exporting Countries. OPEC Bulletin. Organization of the Petroleum Exporting Countries.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.