{HEAD ~ a noise reducing groove} formed at {TAIL ~ an upper surface} of the pump cover and having a predetermined length; and 
formed at
{ HEAD ~ a noise reducing groove } formed at { TAIL ~ an upper surface } of the pump cover and having a predetermined length ; and
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH