Gauge Coupling Unification in Left-Right Symmetric Models
  We explore possibilities of gauge coupling unification in left--right symmetric models with non--minimal particle content. In addition to unification we require the absence of anomalies and sufficient proton lifetime. Numerous previously unknown solutions are presented where unification occurs within the latest experimental errors. Solutions exist where the scale of left--right symmetry breaking can be as low as ${\cal O}(TeV)$ or the scale $M_R$ as high as the Planck scale. 
Manfred Lindner and Manfred Weiser (Technical University of Munich,   Germany)