The co catalyst is initially contacted with {TAIL ~ either} of {HEAD ~ the transition metal catalyst} or the electron donor for a first contact time of 5 120 seconds 
The co catalyst is initially contacted with { TAIL ~ either } of { HEAD ~ the transition metal catalyst } or the electron donor for a first contact time of 5 120 seconds
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH