<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <csymbol cd="linagl1">vector_selector</csymbol> <cn>1</cn> <apply> <csymbol cd="linalg2">matrix</csymbol> <apply> <csymbol cd="linalg2">matrixrow</csymbol> <cn>1</cn> <cn>2</cn> </apply> <apply> <csymbol cd="linalg2">matrixrow</csymbol> <cn>3</cn> <cn>4</cn> </apply> </apply> </apply> </math>