Abstract
In the previous two papers of this series we have applied the spherical tensor formalism to the perturbation treatment of long-range anisotropic forces in a collection of N molecules. In this paper we derive the compact formulas for all categories of the isotropic pairwise additive as well as pair wise non-additive interaction energies which occur in the first three orders of the perturbation theory of long-range forces between N arbitrary molecules. In this way the most important types of the isotropic induction and dispersion pairwise non-additive interactions are taken into account and clearly described.