evel="1" id="a"><span class="secno">1. </span><span class="content">Double-Underline Heading</span><a class="self-link" href="#a"></a></h2>
   <p>text</p>
   <h3 class="heading settled" data-level="1.1" id="b"><span class="secno">1.1. </span><span class="content">Single-Underline Heading</span><a class="self-link" href="#b"></a></h3>
   <p>text</p>
   <h2 class="heading settled" data-level="2" id="c"><span class="secno">2. </span><span class="content">One-Hash Heading</span><a class="self-link" href="#c"></