Primes and subscripts

Hi.

I’m writing some presentation MathML and I’d like to know exatly how I
should write something.  I have a variable x_1 which I represent with
<msub><mi>x</mi><mn>1</mn></msub>.  Now I want to have a variable with
the same name but with a prime after it.  How should I write that?  Both
<msub><mi>x</mi><mn>1</mn></msub><mo>&prime;</mo> and
<msupsub><mi>x</mi><mn>1</mn><mo>&prime;</mo></msupsub> don’t look that
nice in the tool I am using.

Thanks,

Cameron

-- 
Cameron McCormack ≝ http://mcc.id.au/