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