Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/xmltest/valid/sa/044.xml
<!DOCTYPE doc [ <!ELEMENT doc (e*)> <!ELEMENT e EMPTY> <!ATTLIST e a1 CDATA "v1" a2 CDATA "v2" a3 CDATA #IMPLIED> ]> <doc> <e a3="v3"/> <e a1="w1"/> <e a2="w2" a3="v3"/> </doc>