Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/xml-1.1/not-wf/P04a/ibm04an13.xml
<?xml version="1.1" encoding="UTF-8"?> <!DOCTYPE IllegalNameChar← [ <!ELEMENT IllegalNameChar← ANY> ]> <!-- IllegalNameChar #0x2190 --> <IllegalNameChar←/>