Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/valid/P14/ibm14v01.xml
<?xml version="1.0"?> <!DOCTYPE student [ <!ELEMENT student (#PCDATA)> <!ATTLIST student first CDATA #REQUIRED last CDATA #IMPLIED> ]> <!-- testing chardata with empty string --> <student first="Snow"></student>