Four-Neutrino Oscillations
  Models with three active neutrinos and one sterile neutrino can naturally account for maximal oscillations of atmospheric neutrinos, explain the solar neutrino deficit, and accommodate the results of the LSND experiment. The models predict either $\nu_e\to\nu_\tau$ or $\nu_e\to\nu_s$ oscillations in long-baseline experiments with the atmospheric $\delta m^2$ scale and amplitude determined by the LSND oscillations. 
V. Barger