1. R. Kubo andK. Tomita:Journ. Phys. Soc. Japan,9, 888 (1954)
2. A detailed discussion was made by the author in a preliminary report.Busseironkenkyu,89, 79 (1955). A full paper will appear inJourn. Phys. Soc. Japan.
3. See for instanceCallen andWelton:Phys. Rev.,83, 34 (1951).
4. H. Niquist:Phys. Rev.,32, 110 (1928).
5. P. W. Anderson andP. R. Weiss:Rev. Mod. Phys.,25, 316 (1954). The same problem has been discussed in connection whith communication problem, for instance,L. A. Zadeh:Proc. I.R.E.,39, 425 (1951) andZ. Kiyasu:Inst. Elect. Comm. Eng. Japan,34, 605 (1951).