<?xml version="1.0"?>
<!DOCTYPE root SYSTEM "ibm51v02.dtd" [
  <!ELEMENT root ANY>
]>
<root>
  <a> Element type a </a>
  <b> Element type b </b>
  <c> Element type c </c>
  <d> Element type d <c></c> </d>
  <e> Element type e <a></a> <b></b> <c></c> </e>
</root>
<!--* a valid test: tests P51 VC: Proper Group/PE Nesting *-->