1. L. Åsbrink, Phys. Scripta 28, 394 (1983)
2. see also: L. Åsbrink, TRITA-FYS-1001, Physics Department, The Royal Institute of Technology, Stockholm (1980).
3. K. Siegbahn, C. Nordling, A. Fahlman, R. Nordberg, K. Hamrin, J. Hedman, G. Johansson, T. Bergmark, S.-E. Karlsson, I. Lindgren, B. Lindberg, ESCA — Atomic, molecular and solid state structure studied by means of electron spectroscopy, Almqvist and Wixell, Uppsala (1967).
4. K. Siegbahn, C. Nordling, G. Johansson, J. Hedman, P.-F. Hedén, K. Hamrin, U. Gelius, T. Bergmark, L.-O. Werme, R. Manne and Y. Baer, ESCA applied to free molecules, North-Holland, Amsterdam (1969).
5. H. Siegbahn and L. Karlsson, in Handbuch der Physik, Vol. XXXI: Corpuscles and Radiation in Matter I, W. Mehlhorn (ed.), Springer, Berlin (1982), p.215.