Gaya APA

OPEC SURVEY. (). Vienna: OPEC Secretariat.

Gaya Chicago

OPEC SURVEY. . Vienna: OPEC Secretariat, . Text.

Gaya MLA

OPEC SURVEY. . Vienna: OPEC Secretariat, . Text.

Gaya Turabian

OPEC SURVEY. Vienna: OPEC Secretariat, . Print.