<!-- ============= Introduction ============================== -->
-<sect1 id="sec_intro">
+<chapter id="sec_intro">
<title>Introduction</title>
- <sect2 id="what">
+ <sect1 id="what">
<title>What is Matita?</title>
<para>
<application>Matita</application> is a proof assistant for ...
</para>
- </sect2>
-</sect1>
+ </sect1>
+</chapter>