1. N. V. Smith, CRC Critical Reviews in Solid State Sciences, p. 45 (March 1971).
2. P. Görlich and K. Sumi, phys. stat. sol. (b) 2, 427 (1970).
3. W. E. Spicer and R. C. Eden, Proc. 9th Interact. Conf., Physics of Semiconductors, Moscow 1968, vol. 2, p. 65, Izd. Nauka, Leningrad (1968).
4. K. Siegbahn, C. Nordling, A. Fahlman, R. Nordberg, K. Hamrin, J. Hedman, G. Johansson, T. Bergmark, S.-E. Karlsson, I. Lindgren and B. Lindberg, Nova Acta Reg. Soc. Sci. Ups., 20, 1 (1967); also published as: ESCA-Atomic, Molecular and Solid State Structure Studied by Means of Electron Spectroscopy, Almquist and Wiksells, Uppsala (1967).
5. D. W. Turner, C. Baker, A. D. Baker and C. R. Brundle, Molecular Photoelectron Spectroscopy, Wiley and Sons, London (1970).