  We reobtain the Kondo-Doublet interaction by means of the Brillouin-Wigner
Perturbation theory. By applying the same method to the single impurity case we
show that the Kondo-Doublet interaction is a direct consequence of the Kondo
screening cloud. We fully confirm our previous results on this novel
interaction. In particular, we found that for values of the system parameters
typical of semiconductor Quantum Dots heterostructures, the ferromagnetic
Kondo-Doublet interaction dominates over the RKKY one.
