{HEAD ~ Embodiments} of the basic method where vapor only, liquid only, or both liquid and vapor are withdrawn from and returned to the phase contacting {TAIL ~ region} of the distillation system are considered 
{ HEAD ~ Embodiments } of the basic method where vapor only , liquid only , or both liquid and vapor are withdrawn from and returned to the phase contacting { TAIL ~ region } of the distillation system are considered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