% The Cartesian product of two things.
\providecommand*{\cartprod}[2]{ {#1}\times{#2} }
% The Cartesian product of three things.
\providecommand*{\cartprodthree}[3]{ \cartprod{{#1}}{\cartprod{{#2}}{{#3}}} }
% The Cartesian product of two things.
\providecommand*{\cartprod}[2]{ {#1}\times{#2} }
% The Cartesian product of three things.
\providecommand*{\cartprodthree}[3]{ \cartprod{{#1}}{\cartprod{{#2}}{{#3}}} }