1<?xml version="1.0" ?> 2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.0//EN" 3 "/dtd/4.0/docbookx.dtd" [ 4 <!ENTITY subdoc SYSTEM "subdoc.ent"> 5]> 6 7<book lang="en"> 8<title>Main document</title> 9 10<chapter id="main"> 11<para>This references to: <link linkend="subdoc"/></para> 12</chapter> 13&subdoc; 14 15</book> 16