Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/valid/P54/ibm54v03.xml
<?xml version="1.0"?> <!-- test for Production 54--> <!DOCTYPE AttrType [ <!ELEMENT AttrType ANY> <!ELEMENT a (#PCDATA)> <!ATTLIST a att CDATA #IMPLIED> ]> <AttrType> <a att= 'hello world'> </a> </AttrType>