The interesting feature of this Hamiltonian is that the coupling constant between two spins oscillates with distance, therefore it does explain ferro-and antiferromagnetic order observed in rare-earth metals where the direct exchange is negligible. The already mentioned Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction was generalized to a non-spherical Fermi surface by We will present here the most important two edge cases: (1) flat part and (2) cylinder region of the Fermi surface. For the flat part we obtain the following expression for the indirect interaction