Can someone help me to prove the following statement, or introduce some reference about it?
Statement: Suppose that $M$ is a semisimple $R$-module of finite type. There are division rings $D_1, ... , D_r$, such that $End_R(M)$, as a ring, is isomorphism to $\prod_{l=1}^{r} M_{n_l}(D_l)$.
thank you.