<ul>
<li><span style="font-weight: bold;">2009-12.</span> Helena
appears in F. Wiedijk's <a
- href="http://www.cs.ru.nl/%7Efreek/digimath/index.html">index of
+ href="http://www.cs.ru.nl/%7Efreek/digimath/index.html#helena">index of
computer math systems</a>.</li>
</ul>
</li>