The models are selected for the unknown standards and {HEAD ~ performance data} for {TAIL ~ each different calibration standard} of the set are measured by the test system 
for
The models are selected for the unknown standards and { HEAD ~ performance data } for { TAIL ~ each different calibration standard } of the set are measured by the test system
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH