The contribution of the spin-orbit interaction in Hartree-Fock calculation.
for closed-shell nuclei is studied. We obtain explicit expressions for the
finite-range spin-orbit force. New terms with respect to the traditional s
pin-orbit expressions are found. The importance of the finite range is anal
yzed. Results obtained with spin-orbit terms taken from realistic interacti
ons are presented. The effect of the spin-orbit isospin-dependent terms is
evaluated.