{HEAD ~ The electron donor} is added directly to the mixture of the titanium halide and {TAIL ~ the olefin} 
{ HEAD ~ The electron donor } is added directly to the mixture of the titanium halide and { TAIL ~ the olefin }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL