The iteration process continues until {HEAD ~ the predicted values} match {TAIL ~ the measured values} within a desired degree of tolerance 
match
The iteration process continues until { HEAD ~ the predicted values } match { TAIL ~ the measured values } within a desired degree of tolerance
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH