organization of the petroleum exporting countries. (2017). annual report 2017. grasl druck & neue medien gmbh.
Chicago-referens (17:e uppl.)organization of the petroleum exporting countries. Annual Report 2017. austria: grasl druck & neue medien gmbh, 2017.
MLA-referens (9:e uppl.)organization of the petroleum exporting countries. Annual Report 2017. grasl druck & neue medien gmbh, 2017.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.