Unitarity Constraints on Neutrino Mass and Mixings
  We explore the implications of imposing the constraint that two neutrino flavors (which for definiteness we take to be muon and tau neutrinos) are similarly coupled to the mass basis in addition to the unitarity constraints. Implications of this scheme for specific experimental situations are discussed. 
A. B. Balantekin (Wisconsin U., Madison and Max-Planck-Institute,   Heidelberg)