1. R.T. Young, C.W. White, G.J. Clark,J. Narayan,W.H. Christie, M. Murakami, P.W. King, and S.D. Kramer, Appl. Phys. Lett. 32 (1978) 139.
2. S. Hinckley, H. Hora, and J.C. Kelly, Phys. Stat. Solidi 51A (1979) 523.
3. P.D. Maker, R.W. Terhune, and C.M. Savage, Proc. 3rd Int. Quant. Elect. Conf., Paris, February 1963, (N. Bloembergen and M. Grivet, eds.), Dunod, Paris 1964, Vol II, p. 1559.
4. R.G. Meyerand and A.F. Haught, Phys. Rev. Lett. 11 (1963) 401.
5. R. Papoular, Laser Interact. Relat. Plasma Phenomena, (H. Schwarz and H. Hora, eds.), Plenum, New York, 1972, Vol. 2, p. 79.