    <select onchange="groupBy(this.value)">
        <option value="section">Section</option>
        <option value="type">Type</option>
      </select>
    </div>
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="maths_toc" href="#maths">maths</a></li>
<ul class="simple"><li><a class="reference" id="maths-tldr_toc" href="#maths-tldr">TLDR</a></li>
<li><a class="reference" id="maths-links_toc" href="#maths-links">links</a></li>
<li><a class="reference" id="maths-system-procs_toc