Zee-type Neutrino Mass Matrix and Bi-Maximal Mixing
  It is shown that the bi-maximal solution is the only possibility to reconcile Zee-type neutrino mass matrix with three flavors to the current atmospheric and solar neutrino experimental data. The mass of the lightest neutrino, which consist mostly of $\nu_{\mu}$ and $\nu_{\tau}$, is $\simeq \Delta m_{\odot}^2/(2\sqrt{\Delta m_{atm}^2})$. The related topics on Zee-type neutrino mass matrix are also discussed. 
M. Matsuda, C. Jarlskog, S. Skadhauge, M. Tanimoto