1. L.V. Keldysh, 1968, Proc. 9th Int. Conf. Physics Semicon., Moscou (Leningrad, Nauka) pp. 1303–12.
2. For a review on e–h drops see T.M. Rice, J. Hensel, T. Phillips and G.A. Thomas, Solid State Physics, Vol. 32.
3. Electron-Hole Liquids in Semiconductors