  In an improved application of the tetrahedral symmetry A_4 first introduced
by Ma and Rajasekaran, supplemented by the discrete symmetry Z_3 as well as
supersymmetry, a two-parameter form of the neutrino mass matrix is derived
which exhibits the tribimaximal mixing of Harrison, Perkins, and Scott. This
form is the same one obtained previously by Altarelli and Feruglio, and the
inverse of that obtained by Babu and He. If only A_4 is used, then corrections
appear, making tan^2(theta_{12}) differenet from 0.5, without changing
significantly sin^2(2 theta_{23}) from one or theta_{13} from zero.
