Cita APA (7a ed.)

(1991). Facts and figures. Organization of the Petroleum Exporting Countries (OPEC).

Cita Chicago Style (17a ed.)

Facts and Figures. Vienna: Organization of the Petroleum Exporting Countries (OPEC), 1991.

Cita MLA (9a ed.)

Facts and Figures. Organization of the Petroleum Exporting Countries (OPEC), 1991.