1. H. S. W. Massey andE. H. S. Burhop: Electronic and Ionic Impact Phenomena (Oxford, 1956), as alsoR. G. Breene jr.: The Shift and Shape of Spectral Lines (London, 1961).
2. See ref. (1)H. S. W. Massey andE. H. S. Burhop.
3. E. Fermi: NuovoCimento,11, 157 (1934).
4. P. Gombàs:Encyclopedia of Physics, vol. 36 (Berlin, 1956).
5. T. Tietz:Nuovo Cimento,1, 955 (1955).