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