1. 5.1 For a review, see, e.g.: C. D. Jefferies, L. V. Keldysh (eds.): Electron-Hole Droplets in Semiconductors (North-Holland, New York 1983)
2. H. Ehrenreich, F. Seitz, D. Turnbull eds.): Solid State Physics, Vol. 32 Academic, New York 1977)
3. M. Ueta, H. Kanzaki, K. Kobayashi, Y. Toyozawa, E. Hanamura: Excitonic processes in solids, Springer Ser. Solid-State Sci., Vol. 60 (Springer, Berlin, Heideberg 1986).
4. S. Nikitine: In Excitons at High Density, ed. by H. Haken, S. Nikitine (Springer, New York 1975)
5. M. A. Tamor, J. P. Wolfe: Phys. Rev. Lett. 44, 1703 (1980)