“…The energy of the ground state (2.20) (2·21) however, comes out to be very similar to the usual second order result of the perturbation theory and differs from it only by the energy denominator in ,\-hich, in our case, are contained the coupling potentials as can be seen from the definition of Si' Further, the distribution of particles on the energy levels in the grouud state is found to be markedly different from that given by the zeroth approximation, namely all levels are occupied below the Fermi surface and all levels are vacant above this surface, but rather resembles, as has been especially remarked by S. Watanabe,4) to the particle distribution for the finite temperature, which situation-may be quantitatively computable by the evaluation 11]1' (ik, l's) 1 …”