Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/oasis/p76pass1.xml
<!DOCTYPE doc [ <!ELEMENT doc (#PCDATA)> <!NOTATION unknot PUBLIC "Unknown"> <!ENTITY ge SYSTEM "nop.ent" NDATA unknot> <!ENTITY ge2 SYSTEM "nop.ent" NDATA unknot > ]> <doc/>