 Concatenation grammar

For grammars $G=(\Sigma ,V,P,S)$ and $G^{\prime }=(\Sigma ,V^{\prime },P^{\prime },S^{\prime })$ with disjoint variable sets, introduce a new variable $S_0$ and setIf both input grammars are variable based, then $L(H)=L(G)L(G^{\prime })$.