Among the possible operations on the crystal lattice, we can mention A$\backslash$pi $($pi rotation$),$ m $($reflection$)$ and I $($inversion$).$ These three operations are combined as follows: A$\backslash$pi $^2=$m$^2=$i$^2=$I and A$\backslash$pi $.$m$=$i$,$ m$.$i$=$A$\backslash$pi $,$ i$.$A$\backslash$pi $=$m Show that the group $($I$,$A$\backslash$pi $,$m$,$i$)$ is isomorphism with the quartet group