title: Why is this not a valid XML DTD? (Parameter entity and #PCDATA)
body: <p>Using the DTD validator <a href="http://www.validome.org/grammar/validate/" rel="nofollow noreferrer">here</a>, I am informed that the following DTD is invalid.</p>
  
  <pre><code>&lt;!ENTITY % text "(#PCDATA|L)*"&gt;
  &lt;!ELEMENT H         (%text;)+&gt;
  &lt;!ELEMENT L         (#PCDATA)&gt;
  </code></pre>
  
  <p>The error message is: "A '(' character or an element type is required within declaration of element type "H"." at line 2, column 22.</p>
  
  <p>Can anyone please point out why it is invalid?  And how can I make it valid?  The error message is not exactly very friendly to me.  Thanks.</p>