...
<chapter  id="intro"> 1
<title>Introduction</title>
<para>Welcome to our new product. One of its 
new features is a <link  linkend="WidgetIntro">widget</link>.  2
Other new features include ...
</para>
</chapter>
<chapter  id="WidgetIntro">  3
<title>Introducing the Widget</title>
<para>Widgets are just one of our new features.
For a complete list of new features, see <xref  linkend="intro"/>.  4
</para>
</chapter>