[texhax] Lower subscripts

[Barbara Beeton]

    I'm forced to agree, and even adding the apparently
    missing braces doesn't help; the best I can manage is :
    
    	$\rho_{_{{X_1 X_2}}}$

oh, phil, surely you haven't forgotten
that if there's a superscript, the
subscripts are pushed down!

how about this:

  $\rho^{}_{X_1 X_2}$
						-- bb