test/VCM/v23.xml - third_party/libxml2 - Git at Google

 <!DOCTYPE doc [
 <!ELEMENT doc (a?, (b, c?)?, d)>
 <!ELEMENT a EMPTY>
 <!ELEMENT b EMPTY>
 <!ELEMENT c EMPTY>
 <!ELEMENT d EMPTY>
 ]>
 <doc>
 <d/>
 </doc>
	<!DOCTYPE doc [
	<!ELEMENT doc (a?, (b, c?)?, d)>
	<!ELEMENT a EMPTY>
	<!ELEMENT b EMPTY>
	<!ELEMENT c EMPTY>
	<!ELEMENT d EMPTY>
	]>
	<doc>
	<d/>
	</doc>