Necessity is related to Important. Important is related to Rank. Rank is related to Mayor. Mayor is related to Top. 
Prove is derived from Proof. Prove is related to Confirm. 
Necessity <--RelatedTo--> Important <--RelatedTo--> Rank <--RelatedTo--> Mayor <--RelatedTo--> Top 
Proof <--DerivedFrom-- Prove <--RelatedTo--> Confirm 