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