ibm68n10.xml

<!DOCTYPE root 
[
<!ELEMENT root (#PCDATA)>
<!ATTLIST root att CDATA #IMPLIED>
<!--* indirect recursive entity reference *-->
<!ENTITY aaa "&bbb;">
<!ENTITY bbb "&ccc;">
<!ENTITY ccc "&ddd;">
<!ENTITY ddd "&eee;">
<!ENTITY eee "&aaa;">
]>
<root>&aaa;</root>