A content of {HEAD ~ 4.0 percent} by {TAIL ~ weight} is already considered sufficient in every case 
by
A content of { HEAD ~ 4.0 percent } by { TAIL ~ weight } is already considered sufficient in every case
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH