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    Hi Jagath, <br>
    <br>
    mathvariant 'double-struck' is called <i>blackboard bold</i>. There
    are no 'bold double-struck', I believe. <br>
    Therefore <i><mstyle mathvariant="bold"></i> is redundant.<br>
    <pre class="moz-signature" cols="160">
Best regards,
-- 
Deimi
</pre>
    <div class="moz-cite-prefix">On 08/25/2015 08:24 AM, Jagath AR
      wrote:<br>
    </div>
    <blockquote
cite="mid:CANRay2B1HwArw2us9VNjtXQ+xfVBoMWB7Tonf1=Y_+Qakvp9pg@mail.gmail.com"
      type="cite">
      <div dir="ltr">
        <div class="gmail_default" style="color:rgb(51,102,255)">Hi
          Georg,</div>
        <div class="gmail_default" style="color:rgb(51,102,255)">One of
          the easiest way to achieve correct MathML tag for this is to
          use below tex4ht cfg on your MWE:</div>
        <div class="gmail_default" style="color:rgb(51,102,255)"><br>
        </div>
        <div class="gmail_default" style="color:rgb(51,102,255)"><font
            face="monospace, monospace">%-------------------------------------------------------------------</font></div>
        <div class="gmail_default" style="">
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">% htlatex <tex>
              <cfg></font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\RequirePackage{amssymb} %
              used for \mathbb</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\RequirePackage{bm}      %
              used for \boldsymbol</font></div>
          <div class="gmail_default" style=""><br>
          </div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Preamble{xhtml,mathml}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{VERSION}{}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{DOCTYPE}{\HCode{<!DOCTYPE
              html>\Hnewline}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{HTML}{\HCode{<html>\Hnewline}}{\HCode{\Hnewline</html>}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{@HEAD}{}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{@HEAD}{\HCode{<meta
              charset="UTF-8" />\Hnewline}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{@HEAD}{\HCode{<meta
              name="generator" content="TeX4ht</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">(<a moz-do-not-send="true"
                href="http://www.cse.ohio-state.edu/%5Cstring%7Egurari/TeX4ht/">http://www.cse.ohio-state.edu/\string~gurari/TeX4ht/</a>)"
              />\Hnewline}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{@HEAD}{\HCode{<link</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">         rel="stylesheet"
              type="text/css"</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">       
               href="\expandafter\csname aa:CssFile\endcsname"
              />\Hnewline}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{@HEAD}{\HCode{<script
              type="text/javascript"\Hnewline</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">src="<a moz-do-not-send="true"
href="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_SVG">http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_SVG</a>"\Hnewline</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">></script>\Hnewline}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\Configure{@HEAD}{\HCode{<style
              type="text/css">\Hnewline</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">  .MathJax_MathML
              {text-indent: 0;}\Hnewline</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace"></style>\Hnewline}}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\begin{document}</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace">\EndPreamble</font></div>
          <div class="gmail_default" style=""><font color="#3366ff"
              face="monospace, monospace"><br>
            </font></div>
          <div class="gmail_default" style=""><span
              style="color:rgb(51,102,255);font-family:monospace,monospace">\def\mathbbm#1{\boldsymbol{\mathbb{#1}}}</span><br>
          </div>
          <div class="gmail_default" style="">
            <div class="gmail_default" style="color:rgb(51,102,255)"><span
                style="font-family:monospace,monospace">\endinput</span><br>
            </div>
          </div>
          <div style="color:rgb(51,102,255)">
            <div class="gmail_default" style="color:rgb(34,34,34)">
              <div class="gmail_default" style="color:rgb(51,102,255)"><font
                  face="monospace, monospace">%-------------------------------------------------------------------</font></div>
            </div>
          </div>
          <div style="color:rgb(51,102,255)"><br>
          </div>
          <div style="color:rgb(51,102,255)">But still I am only able to
            see normal blackboard font through browser, while the MathML
            is <mstyle
            mathvariant="bold"><mi>&#x2124;</mi></mstyle>.</div>
          <div style="color:rgb(51,102,255)"><br>
          </div>
          <div style="color:rgb(51,102,255)">Regards</div>
          <div style="color:rgb(51,102,255)">Jagath</div>
        </div>
      </div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">On 25 August 2015 at 00:14, Hans Georg
          Schaathun <span dir="ltr"><<a moz-do-not-send="true"
              href="mailto:georg+tex@schaathun.net" target="_blank">georg+tex@schaathun.net</a>></span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin:0 0 0
            .8ex;border-left:1px #ccc solid;padding-left:1ex"><span
              class="">On Mon, Aug 24, 2015 at 08:32:58PM +0200, Michal
              Hoftich wrote:<br>
              > could you please provide some sample document? This
              depends on your<br>
              > input, in particular on used fonts. We can map LaTeX
              font symbols to<br>
              > unicode values, so it shouldn't be impossible to get
              blackboard letters<br>
              > without some custom macros.<br>
              <br>
            </span>Of course here is an example:<br>
            \documentclass{scrartcl}<br>
            \usepackage{bbm}<br>
            \def\Z{\mathbbm{Z}}<br>
            \begin{document}<br>
            $\Z$<br>
            \end{document}<br>
            <br>
            I am not sure what you have in mind.  You are right that
            there is are<br>
            Unicode characters for blackboard bold letters.  A common
            solution<br>
            in LaTeX would however code it as a blackboard bold font.  I
            have not<br>
            checked the implementation of the bbm package, so I do not
            know what<br>
            that one does.<br>
            <br>
            Either way, I am not hellbent on using bbm; any solution
            which works<br>
            in both PDF and XML output is fine.<br>
            <span class="HOEnZb"><font color="#888888"><br>
                <br>
                --<br>
                :-- Hans Georg<br>
              </font></span></blockquote>
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