{HEAD ~ The two sub regions} of center region 34, in an embodiment, are connected together {TAIL ~ external} of the sub regions 
are connected together
{ HEAD ~ The two sub regions } of center region 34 , in an embodiment , are connected together { TAIL ~ external } of the sub regions
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH