<!DOCTYPE html>
<html>
<head>
  <meta charset=utf-8>
  <title>&lt;sup&gt;</title>
</head>
<body>
  <!-- is structured inline -->
  <p><sup class="class" lang="en">text</sup></p>

  <!-- is strictly inline -->
  <p><dfn><sup class="class" lang="en">text</sup></dfn></p>

  <!-- can be empty -->
  <p>text <sup></sup></p>
  <p>text <dfn><sup></sup></dfn></p>

  <!-- can contain interactive -->
  <p><sup><a>text</a></sup></p>
  <p><dfn><sup><a>text</a></sup></dfn></p>

  <!-- cannot contain structured inline -->
</body>
</html>