Gauge Model for Maximal Neutrino Mixing
  The recently announced Super-Kamiokande data on atmospheric neutrino oscillation seems to require a maximal mixing between the $\nu_{\mu}$ and $\nu_{\tau}$ within the conventional three neutrino picture. It is then tempting to suggest as has been done in literature, that the solar neutrino deficit be also understood as resulting from a maximal mixing between $\nu_e$ and $\nu_{\mu}$. In this letter, we propose a left-right symmetric extension of the standard model where permutation symmetry leads to one of the maximal mixing patterns in a technically natural manner. The double seesaw mechanism gives small Majorana masses for neutrinos needed to understand the atmospheric as well as the solar neutrino puzzles. 
R. N. Mohapatra and S. Nussinov