repeating the sequence of steps through with respect to {HEAD ~ subsequent substrate elements} in {TAIL ~ the series} 
in
repeating the sequence of steps through with respect to { HEAD ~ subsequent substrate elements } in { TAIL ~ the series }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL