Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/xml-1.1/invalid/P46/ibm46i01.xml
<?xml version="1.1"?> <!DOCTYPE root [ <!ENTITY int "…"> <!ELEMENT root (a)> <!ELEMENT a EMPTY> ]> <!-- Invalid because NEL and LSEP are not allowed as whitespace. --> <root>∫ <a/> </root>