{HEAD ~ Multi stage process} for {TAIL ~ demetalation}, desulfurization and dewaxing of petroleum oils 
for
{ HEAD ~ Multi stage process } for { TAIL ~ demetalation } , desulfurization and dewaxing of petroleum oils
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH