Symmetrical Parametrizations of the Lepton Mixing Matrix
  Advantages of the original symmetrical form of the parametrization of the lepton mixing matrix are discussed. It provides a conceptually more transparent description of neutrino oscillations and lepton number violating processes like neutrinoless double beta decay, clarifying the significance of Dirac and Majorana phases. It is also ideal for parametrizing scenarios with light sterile neutrinos. 
W. Rodejohann, J. W. F. Valle
hep-ph hep-ex