Creating a link to ‘Tree of Math’

To create a link that looks like this:

Tree of Math

Cut and paste the code below to the desired position in your HTML document:
Feel free to change the text in the clickable area.
If you don't want the link centered, just remove the  <center>  and  </center>  tags.
If you don't want the extra vertical space above and below the link, just remove the  <br />  tags.