Let $R$ be a commutative ring with unity and $M_R$ be a nonzero unital right $R$-module. We say that $M$ is an OI $R$-module if for each $x \in R$, $Mx = M$ implies $x$ is invertible in $R$. We give a characterization of OI torsion abelian groups in terms of their direct summands.
"A Note on OI Torsion Abelian Groups." Missouri J. Math. Sci. 27 (1) 33 - 36, November 2015. https://doi.org/10.35834/mjms/1449161365