ABHYANKAR 82nd BIRTHDAY CONFERENCE SPEAKER: Ignacio Luengo (Madrid) TITLE: Geometric properties of common dicritical of jacobian pairs ABSTRACT: A jacobian pair (f,g) is a pair of polynomials in the plane such that its jacobian Jac(f,g) is constant. We give the structure of the common diacriticals of Jacobian pairs that are not automorphisms. This can be useful for the proof of the Jacobian conjecture of the plane.