<A> <B>	means that <A> can be derived to be <B>
<A> <B>
<C>	means that <A> can be derived to be <B> or <C>

 

( <A> | <B> )	means either <A> or <B>
( <A> )	means <A>
[ <A> ]	means 0 or 1 <A>
( <A> )*	means a sequence of 0 or more instances of <A>
( <A> )+	means a sequence of 1 or more instances of <A>