{HEAD ~ The process} comprises adding an olefin to a titanium halide and then adding {TAIL ~ an electron donor} to the mixture of the olefin and titanium halide 
comprises adding
{ HEAD ~ The process } comprises adding an olefin to a titanium halide and then adding { TAIL ~ an electron donor } to the mixture of the olefin and titanium halide
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH