Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/not-wf/P63/ibm63n03.dtd
<?xml version="1.0" encoding='UTF-8'?> <!-- DTD for Production 63--> <?[IGNORE[ ]]> <!--Negative test with pattern3 of P63--> <!--Wrong Character '?' instead of '!' -->