<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1 plus MathML 2.0//EN" "http://www.w3.org/Math/DTD/mathml2/xhtml-math11-f.dtd" > <html xmlns="http://www.w3.org/1999/xhtml"> <head> </head> <body> <p> <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub> <mi>x</mi> <mn>2</mn> </msub> </math> </p> </body> </html>