Htlatex with docbook-mml: minus signs vanish

Question

When I compile the following file:

\documentclass{article}

\begin{document}
$2-1$
\end{document}

with the command

htlatex test.tex "xhtml,docbook-mml" " -cunihtf" "-cdocbk"

then the result is

<?xml version="1.0"?> 
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook V5.0//EN" 
"http://www.oasis-open.org/docbook/xml/5.0/docbook.dtd" > 

<!--translated from test.tex, on 2015-06-21 22:48:00,  
by TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/) xhtml,docbook-mml,html,refcaption --> 
 <?xtpipes file="docbook.4xt" ?> 

<article
 xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"><title
></title> 

<!--l. 4
--><para><inlineequation role="inline"><!--l. 4
--><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn> <mo class="MathClass-bin"/> <mn>1</mn></math> </inlineequation></para></article>

Obviously, the minus sign vanishes into an empty tag. How can I solve that problem?

Answer 1

The problem can be solved by copying

texmf/tex4ht/ht-fonts/mozilla/charset/unicode.4hf

to the working directory.

The solution was given here:

Defining XML output for operator

and here:

http://web.cse.ohio-state.edu/~gurari/docs/tug-07/tug07-10.xht