svg tref not working

I am new to svg. I can get much of it to work. I am having a problem with tref in a text. If I put the example code from:
https://developer.mozilla.org/en-US/docs/Web/SVG/Element/tref
into a file named tref.svg and drag tref.svg to my Firefox browser (v25.0) I see the "Inline character data", but not "Referenced character data". I get the same results from IE10. If I use Inkscape, I see the "Referenced character data". Is this me or the browser? I have looked at several examples from the web including:
http://www.w3.org/TR/SVG11/text.html#TRefElement
They have a similar example, and I get the same results.

Thanks,
David