1. G.K.Wehner: InMethods of Surface Anaiysis, ed. by A.W.Czanderna (Elsevier Sci. Pub. Co., New Vork 1975) Chap. 1
2. A.Bennighoven: Z. Physik230, 403 (1970)
3. S.Hofmann: Appl. Phys.9, 59 (1976)
4. S.Hofmann: Appl. Phys.13, 205 (1977)
5. Reader may refer to W.Schockley, J.R.Pierce: Proc. Inst. Radio Engrs.26, 3 (1938); and as a textbook, for instante, to