A New Treatment of Neutrino Oscillations in Medium
  A new more rigorous and accurate method for treating neutrino oscillations in the context of the MSW effect in a medium is proposed. This leads to a new type of resonance condition which for small mixing angles puts rather stringent conditions on $E_{\nu}/\delta {m^2}$. The implications on the solar neutrino problem are discussed. 
G.K. Leontaris and J. D. Vergados