Gruppe/Assoziativität/Diagramm

${\begin{matrix}G\times G\times G&{\stackrel {\mu \times \operatorname {Id} _{G}}{\longrightarrow }}&G\times G&\\\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\operatorname {Id} _{G}\times \mu \downarrow &&\downarrow \mu \!\!\!\!\!&\\G\times G&{\stackrel {\mu }{\longrightarrow }}&G&\!\!\!\!\!\\\end{matrix}}$