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