Maintain is a synonym of Assert. Assert is related to Claim. Claim is related to Demand. Demand is related to Economics. 
Pump is a type of Raise. Raise is a type of Express. Voice is a type of Express. Voice is related to Used. 
Maintain <--Synonym--> Assert <--RelatedTo--> Claim <--RelatedTo--> Demand <--RelatedTo--> Economics 
Pump --IsA--> Raise --IsA--> Express <--IsA-- Voice <--RelatedTo--> Used 