Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/not-wf/P46/ibm46n02.xml
<?xml version="1.0"?> <!DOCTYPE root [ <!ELEMENT root (#PCDATA)> <!--* Wrong keyword: Empty in contentspec *--> <!ELEMENT aElement Empty > ]> <root>Any content</root>