<!--
This gets parsed without complaint:
<!ELEMENT pfx:notes  ( #PCDATA | note | pfx:note )* >
-->

<!--
This triggers a diagnostic:
notes.dtd:13: validity error : Definition of notes has duplicate 
references of note
<!ELEMENT pfx:notes  ( #PCDATA | pfx:note | note )* >
-->

<!ELEMENT pfx:notes  ( #PCDATA | pfx:note | note )* >

<!ATTLIST notes
	xmlns:pfx CDATA #FIXED 'http://namespace/uri/here'
>
<!ELEMENT note EMPTY >
<!ELEMENT pfx:note EMPTY >