1. A.B. Pippard, in Advances in Electronics, L. Marton, Academic Press, New York (1954)
2. R.G. Chambers, Proc. Roy. Soc. (London) A215 (1952) p. 481
3. R. Pöpel, Dissertation University of Braunschweig, (1986)
4. A.B. Pippard, Proc. Roy. Soc. (London) A216 (1953) p. 547
5. J. Bardeen, L.N. Cooper, J.R. Schrieffer, Phys. Rev. 108 (1957) p. 1175