{TAIL ~ A non dissolvable region} disposed adjacent to {HEAD ~ the dissolvable region} may optionally be provided 
{ TAIL ~ A non dissolvable region } disposed adjacent to { HEAD ~ the dissolvable region } may optionally be provided
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH