Comparison results for conjugate and focal points in semi-Riemannian   geometry via Maslov index
  We prove an estimate on the difference of Maslov indices relative to the choice of two distinct reference Lagrangians of a continuous path in the Lagrangian Grassmannian of a symplectic space. We discuss some applications to the study of conjugate and focal points along a geodesic in a semi-Riemannian manifold. 
Miguel Angel Javaloyes, Paolo Piccione