Atmospheric Neutrino Problem in Maximally-Mixed Three Generations of   Neutrinos
  Motivated by the indication that both the atmospheric and the solar neutrino puzzles may simultaneously be solved by (vacuum as well as matter-induced resonant) oscillations of two generations of neutrinos with large mixing, we have analyzed the data on the atmospheric and solar neutrinos assuming that all {\it three} neutrinos are maximally mixed. It is shown that the values of $ \Delta m^2 $ obtained from the two-generation analyses are still valid even in the three-generation scheme, i.e. the two puzzles can be solved simultaneously if $ \Delta m_{31}^2 \simeq 10^{-2} \, \mathrm{eV}^2 $ for the atmospheric neutrinos and $ \Delta m_{21}^2 \simeq 10^{-10} \, \mathrm{eV}^2 $ for solar neutrinos in the maximally mixed three-generation scheme. 
C. Giunti, C. W. Kim and J. D. Kim