Added Productions to README.md

README.md

@@ -18,9 +18,21 @@ A Nonterminal starts with a leading `$`. The nonterminal `FOO` would be written
 
 ### Terminals
 
-A Terminals starts with a leading `/`. The terminal `bar` would be written as:
+A Terminal starts with a leading `/`. The terminal `bar` would be written as:
 
     /bar
 
 Note that `/ab` differs from `/a/b`. The string `/ab` resolves to the terminal `ab`,
 whereas `/a/b` resolves to the terminals `a` and `b`
+
+#### Empty String
+
+`/~` resolves to the *Empty String*
+
+
+### Productions
+
+The `->` indicates a production, the *Nonterminal* on it's left side gets replaced
+by the string of *Nonterminals* and *Terminals* on it's right side.
+
+    $FOO -> /foo$FOO