Hierarchical Mass Matrices in a Minimal SO(10) Grand Unification I
  We consider a minimal SO(10) unified model with horizontal Peccei-Quinn symmetry. The hierarchical structure of quark-lepton mass matrices is naturally implemented by the remnants of certain irrelevant terms. Georgi-Jarlskog relations are also realized due to the horizontal symmetry. 
Masako Bando, K.-I. Izawa, and Tomohiko Takahashi