Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/invalid/P39/out/ibm39i04.xml
<root><a></a><b> <c><f></f></c> content of b element <c> <d>not declared in dtd</d> </c> </b></root>