<?xml version='1.0' ?>
<!DOCTYPE test  [
<!ELEMENT test (#PCDATA | inner)*>
<!ELEMENT inner (#PCDATA)>
<!ENTITY t1 "t2=&t2;...">
<!ENTITY t2 "t3=&t3;...">
<!ENTITY t3 "t1=&t1;...">
]>
<test
  ><inner
    >
  Some text: t1=t2=t3=
    <!Error: Recursive substitution of RefEntity "t3">
    ..........
  </inner></test>