For reasons of economy, {HEAD ~ an upper limit} of 5 percent by weight, {TAIL ~ preferably even only 4.5 percent} by weight, should not be exceeded 
of
For reasons of economy , { HEAD ~ an upper limit } of 5 percent by weight , { TAIL ~ preferably even only 4.5 percent } by weight , should not be exceeded
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH