  We consider dynamical effects of additional perturbative forces due to the
non-point mass nature of stars and planets: effects such as quadrupolar
distortion and tidal friction in the systems of exo-planets. It is shown that
these forces should not be neglected while modelling the dynamics of planetary
systems, especially taking into account the undefined real masses of the
planets due to unknown orbital inclinations and the unsatisfactory application
of Keplerian fits to the radial velocity data in multiple planetary systems.
