{HEAD ~ A method} 6 wherein vapor employed as {TAIL ~ a heat source} is withdrawn at a point of feed introduction 
{ HEAD ~ A method } 6 wherein vapor employed as { TAIL ~ a heat source } is withdrawn at a point of feed introduction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