{HEAD ~ A further order} of addition is such that the electron donor is initially contacted with {TAIL ~ the transition metal component} for up to 40 seconds 
{ HEAD ~ A further order } of addition is such that the electron donor is initially contacted with { TAIL ~ the transition metal component } for up to 40 seconds
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH