Dyfyniad APA

organization of the petroleum exporting countries. (2017). annual report 2017. grasl druck & neue medien gmbh.

Dyfyniad Arddull Chicago

organization of the petroleum exporting countries. Annual Report 2017. austria: grasl druck & neue medien gmbh, 2017.

Dyfyniad MLA

organization of the petroleum exporting countries. Annual Report 2017. grasl druck & neue medien gmbh, 2017.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.