Where {HEAD ~ nitration} occurs in {TAIL ~ the voloxidation vessel} 12, the nitration gas can also be the oxidation gas 28 or the used oxidation gas 44 
occurs in
Where { HEAD ~ nitration } occurs in { TAIL ~ the voloxidation vessel } 12 , the nitration gas can also be the oxidation gas 28 or the used oxidation gas 44
OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH