Let $(G,+)$$(G,0,+)$ be an abelian group. Does there always exist a ring with unity $(R,+,\cdot)$$(R,0,1,+,\cdot)$ and an injective homomorphism of groups $ \psi:G\rightarrow R$$ \psi:(G,0,+)\rightarrow (R,0,+)$?
Is this hard to prove, or are there simple proofs?