Oil is related to Controversy. Controversy is a type of Dispute. 
Contrast is a type of Differ. Contrast is a type of Scope. Scope is a type of Extent. Limit is a type of Extent. 
Oil <--RelatedTo--> Controversy --IsA--> Dispute 
Differ <--IsA-- Contrast --IsA--> Scope --IsA--> Extent <--IsA-- Limit 