1. Chang C. C., Surface Science25 (1971), 53.
2. Taylor N. J.,in Techniques of Metal Research, Vol. VII, (Ed. R. F. Bunshah) Interscience, New York 1971.
3. Chung M. F., Jenkins L. H., Surface Science22 (1970), 479.
4. Bauer E., Z. Phys.224 (1969), 19.
5. Siegbahn K. et al., ESCA, Atomic, Molecular and Solid State Structure Studied by Means of Electron Spectroscopy, Almquist and Wiksell Boktryckeri AB, Uppsala 1967.