Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/libraries/HaXml/tests/xml-conformance/sun/invalid/attr07.xml
<!DOCTYPE arbor [ <!ELEMENT arbor EMPTY> <!ATTLIST arbor type (fruit | vegetable) "fruit" > <!-- tests the 'must match one of the nmtokens included in the declaration' part of the "Enumeration" VC --> ]> <arbor type="money"/>