Neutrino Masses from Gauge Symmetries
  A very simple extension of the standard model to include an Abelian family symmetry is able to describe the hierarchy of quark and lepton masses and their mixing angles together with the unification of gauge couplings. We consider the implications of this model for neutrino masses and mixing angles and show that they are determined up to a discrete ambiguity corresponding to the representation content of the Higgs sector responsible for the Majorana mass matrix. 
H. Dreiner, G.K. Leontaris, S. Lola, Graham G. Ross and C. Scheich