1. H.-J. Kluge, in:Progress in Atomic Spectroscopy, Part B, ed. W. Hanle and H. Kleinpoppen (Plenum Press, New York and London, 1979) Chap. 17.
2. R. Neugart, in:Progress in Atomic Spectroscopy, Part D, ed. H.J. Beyer and H. Kleinpoppen (Plenum Press, New York and London, 1987) Chap. 2.
3. E.-W. Otten, in:Treatise on Heavy Ion Science, Vol. 8, ed. D.A. Bromley (Plenum Press, New York and London, 1990) p. 517.
4. E.-W. Otten, in:Hyperfine Interactions in Excited Nuclei, Proc. Int. Conf. on Hyperfine Interactions, Rehovot and Jerusalem, 1970, ed. G. Goldring and R. Kalish (Gordon and Breach, New York, 1971) p. 363; see also ref. [1].
5. E. Arnold, J. Bonn, R. Gegenwart, W. Neu, R. Neugart, E.-W. Otten, G. Ulm and K. Wendt, Phys. Lett. B59(1987)771; P. Lievens, Contribution to the International Symposium on Lasers in Nuclear Physics, September 9–10, 1991 (RIKEN, Tokyo).