Ternary Plots for Neutrino Mixing Visualization
  The visualization advantages of ternary plots are illustrated for the PMNS neutrino mixing matrix. Unitarity constraints are incorporated automatically, in part, since barycentric plots of this type allow three variables with a fixed sum to be plotted as mere points inside an equilateral triangle on a plane. 
Cosmas K. Zachos
hep-ph hep-ex