1. Berg, H.F., Ali, A.W., Lincke, R., and Griem, H.R.: 1962, Phys. Rev. Letters 125, 199.
2. Greig, J.R., Griem, H.R., Jones, L.A., and Oda, T.: 1970, Phys. Rev. Letters 24, 3.
3. Griem, H.R.: 1966, Proceedings of the Seventh International Conference on Phenomena in Ionized Gases, Vol. II (Gradevinska Knyga Publishers, Belgrade, p. 551).
4. Jones, L. A., Greig, J. R., Oda, T., and Griem, H. R.: 1971, Phys. Rev. 4, 833.