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