+\providecommand*{\pair}[2]{ \left({#1},{#2}\right) }
+
+% 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}}} }