Predicting the tauon mass as well as the ratio of electron and muon   masses
  Treating the Koide equation and another efficient charged-lepton mass formula (having the form of a mass sum rule) as a system of two mathematically independent algebraic equations for three charged-lepton masses, we predict the tauon mass as well as the ratio of electron and muon masses, both consistent with experiment. 
Wojciech Krolikowski