Organization of Petroleum Exporting Countries. OPEC bulletin. Organization of the Petroleum Exporting Countries.
Чикаго-гийн эшлэл (17 дахь хэвлэлт)Organization of Petroleum Exporting Countries. OPEC Bulletin. Vienna, Austria: Organization of the Petroleum Exporting Countries.
MLA -ийн эшлэл (9 дэх хэвлэлт)Organization of Petroleum Exporting Countries. OPEC Bulletin. Organization of the Petroleum Exporting Countries.
Анхааруулга: Эдгээр ишлэлүүд үргэлж 100% үнэн зөв биш байж магадгүй.