Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/ibm/xml-1.1/not-wf/P77/ibm77n21.dtd
<![INCLUDE [ <!ENTITY % e SYSTEM "ibm77n21.ent"> <!ELEMENT root ANY> %e; ]]>