From Prototype SU(5) to Realistic SU(7) SUSY GUT
  We construct a realistic SU(7) model which provides answers to many questions presently facing the prototype SU(5) SUSY GUT. Among them are a solution to the doublet-triplet splitting problem, string scale unification, proton decay, the hierarchy of baryon vs lepton number violation and neutrino masses. 
J.L. Chkareuli (Tbilisi, Inst. Phys.), C.D. Froggatt (Glasgow U.),   I.G. Gogoladze (Tbilisi, Inst. Phys. & ICTP, Trieste), ...