Thus, retailers obtain {HEAD ~ full price} for {TAIL ~ products} purchased with the exchange system coupons 
for
Thus , retailers obtain { HEAD ~ full price } for { TAIL ~ products } purchased with the exchange system coupons
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH