The paths in each group are then ordered according to the number of {HEAD ~ nodes} in {TAIL ~ each path}, wherein the path with the lowest number of nodes is placed first 
in
The paths in each group are then ordered according to the number of { HEAD ~ nodes } in { TAIL ~ each path } , wherein the path with the lowest number of nodes is placed first
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH