For some reason, the preface mentions just six of the seven major parts

of the book.  Fix it.

doc/src/sgml/intro.sgml

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+$Header: /cvsroot/pgsql/doc/src/sgml/intro.sgml,v 1.23 2003/10/21 22:47:54 tgl Exp $
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 <preface id="preface">
@@ -73,6 +73,13 @@ $Header: /cvsroot/pgsql/doc/src/sgml/intro.sgml,v 1.22 2003/09/11 21:42:20 momji
      program.
     </para>
    </listitem>
+
+   <listitem>
+    <para>
+     <xref linkend="internals"> contains assorted information that can be of
+     use to <productname>PostgreSQL</> developers.
+    </para>
+   </listitem>
   </itemizedlist>
  </para>