{HEAD ~ A method} 6 wherein {TAIL ~ vapor} employed as a heat source is withdrawn at a point of feed introduction 
{ HEAD ~ A method } 6 wherein { TAIL ~ vapor } employed as a heat source is withdrawn at a point of feed introduction
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH