you are likely to find Government in/at/on Civilization. Government is related to Treaty. Treaty is related to International. 
Plastic is a different concept from Metal. Metal is related to Material. Material is related to Oil. Oil is related to Iraqi. 
Civilization <--AtLocation-- Government <--RelatedTo--> Treaty <--RelatedTo--> International 
Plastic <--DistinctFrom--> Metal <--RelatedTo--> Material <--RelatedTo--> Oil <--RelatedTo--> Iraqi 