1. P. Kocian: J. Non-Cryst. Solids 36, 195 (1980)
2. A. von Engel: Electric Plasmas: Their Nature and Uses( Taylor and Francis, London 1983 )
3. G. Herzberg: Atomic Spectra and Atomic Structure( Dover, New York 1944 )
4. J.S. Chang, R.M. Hobson, Y. Ichikawa, T. Kaneda: Atomic and Molecular Processes in Ionized Gases( Tokyo Denki University, Tokyo 1982 )
5. J.K. Franklin, J.G. Dillard, H.M. Rosenstock, J.T. Herron, K. Draxl, F.H. Field: Ionization Potentials, Appearance Potentials, and Heats of Formation of Gaseous Positive Ions; NSRDS-NBS 26 ( US Government Printing Office, Washington, DC 1969 )