Two sterile neutrinos as a consequence of matter structure
  An algebraic argument based on a series of generalized Dirac equations, truncated by an "intrinsic Pauli principle", shows that there should exist two sterile neutrinos as well as three families of leptons and quarks. Then, the influence of these additional neutrinos on neutrino oscillations is studied. As an example, a specific model of effective five-neutrino texture is proposed, where only the nearest neighbours in the sequence of five neutrinos ordered as $\nu_s, \nu'_s, \nu_e, \nu_\mu, \nu_\tau$ are coupled through the 5x5 mass matrix. Its diagonal elements are taken as negligible in comparison with its nonzero off-diagonal entries. 
Wojciech Krolikowski (Warsaw University)