{HEAD ~ Embodiments} of {TAIL ~ the basic method} where vapor only, liquid only, or both liquid and vapor are withdrawn from and returned to the phase contacting region of the distillation system are considered 
of
{ HEAD ~ Embodiments } of { TAIL ~ the basic method } where vapor only , liquid only , or both liquid and vapor are withdrawn from and returned to the phase contacting region of the distillation system are considered
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH