forming {TAIL ~ a first difference} which is {HEAD ~ a function} of the actual temperature and the first model temperature 
forming { TAIL ~ a first difference } which is { HEAD ~ a function } of the actual temperature and the first model temperature
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH