--- a/intro.xmlf
+++ b/intro.xmlf
@@ -1,13 +1,9 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!DOCTYPE book [
-<!ENTITY % eclent SYSTEM "ecl.ent">
-%eclent;
-]>
-<book xmlns="http://docbook.org/ns/docbook" version="5.0" xml:lang="en">
- <preface xml:id="preface">
+<?xml version="1.0"?><!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1//EN" "http://www.oasis-open.org/docbook/xml/4.1/docbookx.dtd">
+<book lang="en">
+ <preface id="preface">
   <title>Preface</title>
 
-  <section xml:id="preface.words">
+  <section id="preface.words">
    <title>About this book</title>
 
    <para>This manual is part of the &ECL; software system. It documents
@@ -41,7 +37,7 @@
    <important><para>Missing highlights</para></important>
   </section>
 
-  <section xml:id="preface.what.is.ecl">
+  <section id="preface.what.is.ecl">
    <title>What is &ECL;?</title>
 
    <para>&ECL; is an implementation of the Common-Lisp language that was
@@ -75,7 +71,7 @@
    with &Steele84; and the corresponding chapter will be updated to
    document <emphasis>only</emphasis> the differences with &ANSI;.</para>
 
-   <section xml:id="Credits">
+   <section id="Credits">
     <title>Credits</title>
     <para>The &ECL; project is an implementation of the Common-Lisp language that aims to
     comply with the ANSI Common-Lisp standard. The first ECL implementations were developed
@@ -133,7 +129,7 @@
     Koivisto and Jeff Bowden, and others whose name I may have omitted.</para>
    </section>
 
-   <section xml:id="Copyright">
+   <section id="Copyright">
     <title>Copyright</title>
     <para role="continues">Copyright &copy; 2000 Juan Jose Garcia Ripoll</para>
     <para role="continues">Copyright &copy; 1990, 1991, 1993 Giuseppe Attardi</para>
@@ -196,7 +192,7 @@
     </blockquote>
    </section>
 
-   <section xml:id="Building-ECL">
+   <section id="Building-ECL">
     <title>Building ECL</title>
     <orderedlist numeration="arabic">
      <listitem>
@@ -227,7 +223,7 @@
       give to configure alternate places.  Try <literal>./configure --help</literal> for
       instructions on how to supply this information to configure, but
       a good starting point is<screen>
-      $ ./configure --prefix=$HOME
+      $ ./configure &ndash;prefix=$HOME
       </screen></para>
      </listitem>
      <listitem>
@@ -300,7 +296,7 @@
     command <literal>make clean</literal>.</para>
    </section>
 
-   <section xml:id="Invoking-ECL">
+   <section id="Invoking-ECL">
     <title>Entering and leaving &ECL;</title>
     <para>&ECL; is invoked by the command <literal>ecl</literal>.</para>
     <para><screen>
@@ -356,7 +352,7 @@
     <para>You can disable ^D as the exit command by setting to <literal>T</literal> the
     following variable:</para>
     <blockquote>
-     <screen><indexterm role="vr"><primary>*ignore-eof-on-terminal-io*</primary></indexterm>&#151; System: <varname>*ignore-eof-on-terminal-io*</varname></screen>
+     <screen><indexterm role="vr"><primary>*ignore-eof-on-terminal-io*</primary></indexterm>&mdash; System: <varname>*ignore-eof-on-terminal-io*</varname></screen>
      <para>This variable controls whether an end of file character (normally ^D)
      should terminate the session. The default value is ().</para>
     </blockquote>