Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/xmltest/valid/sa/095.xml
<!DOCTYPE doc [ <!ATTLIST doc a1 CDATA #IMPLIED> <!ATTLIST doc a1 NMTOKENS #IMPLIED> <!ELEMENT doc (#PCDATA)> ]> <doc a1="1 2"></doc>