Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/not-wf/P49/ibm49n05.xml
<?xml version="1.0"?> <!DOCTYPE root [ <!ELEMENT root (#PCDATA)> <!ELEMENT a ANY> <!ELEMENT b ANY> <!--* extra separator in choice *--> <!ELEMENT aElement (a ||b)* > ]> <root>Any content</root>