Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/not-wf/P71/ibm70n01.xml
<!DOCTYPE root [ <!ELEMENT root (#PCDATA)> <!ATTLIST root att CDATA #IMPLIED> <!ENTITY aaa "aString"> <!--* mess up Entity Declaration *--> <root/> <!ENTITY % paaa "aString"> ]> <root/>