<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <csymbol cd="set1">cartesian_product</csymbol> <csymbol cd="setname1">R</csymbol> <csymbol cd="setname1">R</csymbol> <csymbol cd="setname1">R</csymbol> </apply> </math>
Author: MathML 2 Recommendation