Neutrino Mixing: $A_4$ Variations

In the context of the non-Abelian discrete symmetry $A_4$, the neutrino mass matrix has been studied extensively. A brief update is presented to focus on the conceptual shift from tribimaximal mixing (${\theta }_{13}=0$, $\theta_{23} = \pi/4$,$\tan^2 \theta_{12} = 1/2$)to$\underline{\rm cobimaximal}$ mixing (${\theta }_{13}\mathrm{\ne }0$, ${\theta }_{23}=\pi \mathrm{/}4$, ${\delta }_{CP}=\pm \pi \mathrm{/}2$) which agrees well with present data. Three specific realistic examples are proposed, two with three and the third with just two parameters.