Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/eduni/xml-1.1/043.xml
<?xml version="1.1" encoding="iso-8859-1"?> <!-- Contains a character reference to a C0 control character (form-feed), legal in XML 1.1 but not 1.0 --> <!DOCTYPE foo [ <!ELEMENT foo ANY> ]> <foo></foo>