{HEAD ~ The buffer element} 14 has {TAIL ~ a first edge} 141 and a second edge 142 disposed oppositely to each other 
has
{ HEAD ~ The buffer element } 14 has { TAIL ~ a first edge } 141 and a second edge 142 disposed oppositely to each other
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH