On Fermion Mass Hirerachies in MSSM-like Quiver Models with Stringy   Corrections
  Using instanton effects, we discuss the problem of fermion mass hierarchies in an MSSM-like Type IIA orientifolded model with U(3)xSp(1)xU(1)xU(1) gauge symmetry obtained from intersecting D6-branes. In the corresponding four-stack quiver, the different scales of the generated superpotential couplings offer a partial solution to fermion mass hierarchies. Using the known data with neutrino masses m_{v_{\tau}}\lesssim 2 eV, we give the magnitudes of the relevant scales. 
A. Belhaj, M. Benhamza, S.E. Ennadifi, S. Nassiri, E.H. Saidi
hep-th