{HEAD ~ An important role} for obtaining this result is played by {TAIL ~ the arcuate shape} 16 of the bottom 9 of trough 8 
is played by
{ HEAD ~ An important role } for obtaining this result is played by { TAIL ~ the arcuate shape } 16 of the bottom 9 of trough 8
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH