title: Are nested copybooks allowed in COBOL?
body: <p>I know that many COBOL compilers do allow nested copybooks (with a different depth), but I did not found any "official" rule.
  Questions:</p>
  
  <ol>
  <li><p>Is there any COBOL standard explicit allowing or forbidding nested copybooks?</p></li>
  <li><p>Is there any COBOL compiler not allowing nested copybooks?</p></li>
  </ol>