The selection of heat source vapors and {TAIL ~ heat sink liquid} is such that at least one is withdrawn from the phase contracting region of {HEAD ~ the distillation system} 
The selection of heat source vapors and { TAIL ~ heat sink liquid } is such that at least one is withdrawn from the phase contracting region of { HEAD ~ the distillation system }
OTH OTH OTH OTH OTH OTH OTH TAIL 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