On the Nilpotent Multiplier of a Free Product
  In this paper, using a result of J. Burns and G. Ellis (Math. Z. 226 (1997) 405-28.), we prove that the $c$-nilpotent multiplier (the Baer-invariant with respect to the variety of nilpotent groups of class at most $c$, ${\cal N}_c$.) {\it does commute} with the free product of cyclic groups of mutually coprime order. 
Behrooz Mashayekhy
math.GR