I'm trying to understand the equivalence in expressive power of formal grammars whose rules take the form:
$$ \alpha \rightarrow \beta $$ where $ |\alpha| \leq |\beta| $ (called a monotonic grammar), and grammars whose rules take the form:
$$ \alpha B \gamma \rightarrow \alpha C \gamma $$
where $\alpha $ and $\gamma$ are strings of terminals & non-terminals or possibly empty, and $B$ and $C$ are single non-terminals. I understand that grammars of the second kind are already, by definition, grammars of the first kind, but I'd like to understand how to derive a grammar of the second kind, given one of the first kind (a monotonic grammar). Can anyone suggest a good reference for this? Many thanks in advance.