test/dtd8 - platform/external/libxml2 - Gitiles

 <!DOCTYPE doc [
 <!ELEMENT doc ((a | b) , (c | d))+>
 <!ELEMENT a (#PCDATA)>
 <!ELEMENT b (#PCDATA)>
 <!ELEMENT c (#PCDATA)>
 <!ELEMENT d (#PCDATA)>
 ]>
 <doc><b>This</b><c> is a valid document</c></doc>
	<!DOCTYPE doc [
	<!ELEMENT doc ((a \| b) , (c \| d))+>
	<!ELEMENT a (#PCDATA)>
	<!ELEMENT b (#PCDATA)>
	<!ELEMENT c (#PCDATA)>
	<!ELEMENT d (#PCDATA)>
	]>
	<doc><b>This</b><c> is a valid document</c></doc>