HTML entities ≤ and ≥ result in questionmarks in rendered pdf.

Hi,

we have an issue with ≤ and ≥

example code:

<html>
 <head> 
  <title>Neue HTML Datei</title> 
  <style type="text/css">
  body {
    color: black; background-color: white;
    font-size: 100.01%;
    font-family: Helvetica,Arial,sans-serif;
    margin: 0; padding: 1em;
  }

  div#Inhalt {
    margin-left: 1em;
    padding: 0 1em;
    border: 1px solid #dddddd;
	width: 170mm;
  }
  div#Inhalt #title {
    font-size: 1.5em;
    margin: 0 0 1em;
  }
</style> 
 </head> 
 <body> 
  <div> 
   <div>
    etrewr ౷ 
   </div> Kurzbeschreibung:
   <br />
   <p></p> 
   <p>@@@@@ ≤ ≥</p> 
  </div>  
 </body>
</html>

Thanks a lot for an advice or ideas