<!DOCTYPE HTML> <html> <body> <!-- Stretchy fences --> <math> <mfenced> <mtable> <mtr> <mtd><mi>a</mi></mtd> <mtd><mi>b</mi></mtd> </mtr> <mtr> <mtd><mi>c</mi></mtd> <mtd><mi>d</mi></mtd> </mtr> </mtable> </mfenced> </math> </body> </html>