Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/valid/P28/ibm28v01.xml
<?xml version="1.0" encoding='UTF-8'?> <!DOCTYPE animal [ <!ELEMENT animal EMPTY> ]> <!-- This a valid test file for production [28] --> <animal/>