However, it must be emphasized that these chemical mechanisms are theoretical and the extent to which any one of these mechanisms may be responsible for {HEAD ~ the effectiveness} of {TAIL ~ a sacrificial agent} is unknown 
of
However , it must be emphasized that these chemical mechanisms are theoretical and the extent to which any one of these mechanisms may be responsible for { HEAD ~ the effectiveness } of { TAIL ~ a sacrificial agent } is unknown
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH