  In the paper (Osaka J. Math. {\bf 46}: 403-409, 2009), Yang conjectured that
a non-elementary subgroup $G$ of $SL(2, \bc)$ containing elliptic elements is
discrete if for each elliptic element $g\in G$ the group $< f, g >$ is
discrete, where $f\in SL(2,\bc)$ is a test map which is loxodromic or elliptic.
The purpose of this paper is to give an affirmative answer to this question.
