1. Abrikosov, A.A., Gor'kov, L.P. and Dzyaloshinski, I.E.: 1963,Methods of Quantum Field Theory in Statistical Physics, Dover, N.Y., �21.
2. Arponen, J.: 1972,Nucl. Phys. A 191, 257.
3. Baym, G., Bethe, H.A. and Pethick, C. J.: 1971,Nucl. Phys. A 175, 225.
4. Bethe, H.A., B�rner, G. and Sato, K.: 1970,Astron. Astrophys. 7, 279.
5. Buchler, J.R., and Barkat, Z.: 1971,Phys. Rev. Lett. 27, 48.