What is the backward-compatible method of turning a circle in an SVG into a link?
<html:a href="/our-circle/"><circle cx="10" cy="10" r="5"/></html:a>
<a svg:href="/our-circle/"><circle cx="10" cy="10" r="5"/></a>
<a href="/our-circle/"><circle cx="10" cy="10" r="5"/></a>
<a href="/our-circle/" xlink:href="/our-circle/"><circle cx="10" cy="10" r="5"/></a> Source
<a href="/our-circle/" xlink:href="/our-circle/"><circle cx="10" cy="10" r="5"/></a>