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