1. R. Zimmermann, Many Particle Theory of Highly Excited Semiconductors ( Teubner, Leipzig, 1984 )
2. K. Omidvar, Phys. Rev. 140 (1965) A 26
3. D. Kremp, M. Schlanges, T. Bornath, Phys. stat. sol. (b) 147 (1988) 747
4. M. Schlanges, Th. Bornath, D. Kremp, Phys. Rev. A 88 (1988) 2174
5. W. Ebeling, I. Leike, U. Leonhardt, 8th Am. Phys. Soc. Conf. Atomic Processes in Plasmas ( Portland, Maine, 1991 )