<math> <merror> <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"> <head> <title>MathML's Hello Square</title> </head> <body> <p> This is a perfect square:</p> <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msup> <mfenced> <mrow> <mi>a</mi> <mo>+</mo> <mi>b</mi> </mrow> </mfenced> <mn>2</mn> </msup> </mrow> </math> </body> </html> </merror> </math>