Eq. 8 indicates the values A to Z and {HEAD ~ AA} to {TAIL ~ AE} 
to
Eq . 8 indicates the values A to Z and { HEAD ~ AA } to { TAIL ~ AE }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL