{HEAD ~ A plurality} of mass gas flow controllers are arranged to control {TAIL ~ flow} into a respective inlet port 
{ HEAD ~ A plurality } of mass gas flow controllers are arranged to control { TAIL ~ flow } into a respective inlet port
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH