A sterile neutrino scenario constrained by experiments and cosmology
  We discuss a model in which three active and one sterile neutrino account for the solar, the atmospheric and the LSND neutrino anomalies. It is shown that if $N_\nu<4$ then these and other experiments and big bang nucleosynthesis constrain all the mixing angles severely, and allow only the small-angle MSW solution. If these neutrinos are of Majorana type, then negative results of neutrinoless double beta decay experiments imply that the total mass of neutrinos is not sufficient to account for all the hot dark matter components. 
Nobuchika Okada and Osamu Yasuda