$$r\left( {^ * } \right) = r{}^ * $$

$$\left( {r{}^ * s{}^ * } \right){}^ * = \left( {r + s} \right){}^ * $$

$$\,\left( {r + s} \right){}^ * = r{}^ * + s{}^ * $$

$$r{}^ * s{}^ * = r{}^ * + s{}^ * $$