Pound is related to Weight. Gas have Weight. Gas is related to Natural. Natural is related to River. 
Free is related to Shade. Shade is a synonym of Shadow. Shadow is related to Face. Face is related to Doll. 
Pound <--RelatedTo--> Weight <--HasA-- Gas <--RelatedTo--> Natural <--RelatedTo--> River 
Free <--RelatedTo--> Shade <--Synonym--> Shadow <--RelatedTo--> Face <--RelatedTo--> Doll 