{HEAD ~ A catalyst} obtained by contacting a compound of a transition metal of the group V of the Periodic Table represented by {TAIL ~ formula} : 
represented by
{ HEAD ~ A catalyst } obtained by contacting a compound of a transition metal of the group V of the Periodic Table represented by { TAIL ~ formula } :
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH