Thank you all very much for the input. Yes, the copy-of did

> the trick.  Now I am trying to usng FOP redering as follows..
>  I see no FO effect. I muct be doing something silly but, don't know what.

FO is not the same as HTML. In order to get a
subscript in FO, you'll have to produce something
like
 <fo:inline vertical-align="sub">testsub</fo:inline>