ABSTRACT
As is well-known, it is not possible to account for all three neutrino anomalies with just the three known neutrinos (ve, V /-L and vT ), If one or more of them can be explained in some other way, then no extra sterile neutrinos need be invoked. This is one motivation for exotic scenarios. In any case it is important to rule out all explanations other than oscillations in order to establish neutrino mixing and oscillations as the unique explanation for the three observed neutrino anomalies.
