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