1. J. Lapujoulade, Y. Lejay: J. de Phys. 38, L303 (1977)
2. Y. Lejay, J. Lapujoulade:Proc. 7th Int. Vacuum Congr. and 3rd Int. Conf. on Solid Surfaces ed. by R. Dobrzemski, F. Rüdenauer, F.P. Viebock, A. Breth (Vienna 1977 ) p. 1373
3. J. Lapujoulade: Surf. Sci. 108, 526 (1981)
4. R. Spadacini, C.E. Tommei: Surf. Sci. 133, 216 (1983)
5. A.C. Levi: Surf. Sci. 137, 305 (1984)