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