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