{TAIL ~ Any method} of {HEAD ~ estimation} may, of course, be adopted provided that the method has practically sufficient accuracy 
{ TAIL ~ Any method } of { HEAD ~ estimation } may , of course , be adopted provided that the method has practically sufficient accuracy
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH