The Natural Lift Curves for the Spherical Indicatrices of the   Timelike-Spacelike Bertrand Couple in Minkowski 3-Space
  This paper deals with the natural lift curves and the geodesic sprays for the spherical indicatrices of the timelike-spacelike Bertrand couple on the tangent bundle or in Minkowski 3-space and then give some new characterizations for these curves. Additionally we illustrate an example of our main results. 
M. Bilici, E. Ergun, M. Caliskan
math.DG