Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/not-wf/P72/ibm72n03.xml
<!DOCTYPE root [ <!ELEMENT root (#PCDATA)> <!ATTLIST root att CDATA #IMPLIED> <!--* missing space *--> <!ENTITY % paaa"<!-- comments -->"> %paaa; ]> <root/>