The mass flow controllers 74 and 76 control {TAIL ~ the flow rates} of {HEAD ~ the silane phosphine mixture} 
The mass flow controllers 74 and 76 control { TAIL ~ the flow rates } of { HEAD ~ the silane phosphine mixture }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD