can be used.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="docguide-style-ref-pages-exit-status">
      <term>Exit Status</term>
      <listitem>
       <para>
        If the program uses 0 for success and non-zero for failure,
        then you do not need to document it.  If there is a meaning
        behind the different non-zero exit codes, list them here.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="docguide-style-ref-pages-usage">
      <term>Usage</term>
      <listitem>
       <para>
        Describe any sublanguage or run-time interface of the program.
        If the program is not interactive, this section can usually be
        omitted.  Otherwise, this section is a catch-all for
        describing run-time features.  Use subsections if appropriate.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="docguide-style-ref-pages-environment">
      <term>Environment</term>
      <listitem>
       <para>
        List all environment variables that the program might use.
        Try to be complete; even seemingly trivial variables like
        <envar>SHELL</envar> might be of interest to the user.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="docguide-style-ref-pages-files">
      <term>Files</term>
      <listitem>
       <para>
        List any files that the program might access implicitly.  That
        is, do not list input and output files that were specified on
        the command line, but list configuration files, etc.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="docguide-style-ref-pages-diagnostics">
      <term>Diagnostics</term>
      <listitem>
       <para>
        Explain any unusual output that the program might create.
        Refrain from listing every possible error message.  This is a
        lot of work and has little use in practice.  But if, say, the
        error messages have a standard format that the user can parse,
        this would be the place to explain it.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="docguide-style-ref-pages-notes">
      <term>Notes</term>
      <listitem>
       <para>
        Anything that doesn't fit elsewhere, but in particular