Free products of abelian groups in the unit group of integral group rings

Proc. Amer. Math. Soc. 126 (1998), 1257-1265.

Eric Jespers
Department of Mathematics and Statistics, Memorial University of Newfoundland, 
St. John's, Newfoundland, Canada A1C 5S7 
 
and Guilherme Leal
Instituto de Matem\`atica, Universidade Federal do Rio de Janeiro, 
Rio de Janeiro RJ, Brazil 

Abstract. We classify finite groups G which are such that the unit group of 
the integral group ring ZG has a subgroup of finite index which is a 
non-trivial free product of abelian groups.