{TAIL ~ A mixture} of silane, phosphine and boron trichloride is flowed into the reactor tube through {HEAD ~ a first pair} of silane injectors 
{ TAIL ~ A mixture } of silane , phosphine and boron trichloride is flowed into the reactor tube through { HEAD ~ a first pair } of silane injectors
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH