Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/not-wf/P56/ibm56n06.xml
<?xml version="1.0"?> <!-- test for Production 56--> <!DOCTYPE root [ <!ELEMENT root ANY> <!ELEMENT a EMPTY> <!ATTLIST a attr NMtokens #REQUIRED> ]> <root> Invalid TokenizedType NMtokens(case sensitive) </root>