Michel Henon's first research article: An improved calculation of the
  perturbation of stellar velocities
  Fifteen years after the discovery of dynamical friction by Chandrasekhar,
Michel Henon attempts to solve the longstanding problem of the divergence of
the friction suffered by the perturber and caused by the most distant cluster
stars. His solution laid the foundation to the current understanding of
dynamical friction as a non-local transitory force.
