<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE  somedoc [
  <!ENTITY a   "something">
  <!ENTITY b   "&a;">
]>

<somedoc>

<somebeacon someattribute="&b;"/>

&a; should appear after colon: &a;
&b; should appear after colon: &a;
&a; should appear after colon: &b;
&b; should appear after colon: &b;

</somedoc>