Constructing the ultimate theory of grand unification
  In accordance with known phenomenological facts on leptons and quarks in the Standard Model as well as on the scale of neutrino masses and introducing the supersymmetry, we logically substantiate the unique composition of fundamental representation for the fermionic multiplet of gauge group $E_8$. 
V.V.Kiselev, V.V.Shakirov
hep-ph