[1] He D, Hall D R.J A P, 1984; 56:856
[2] Vidand P,He D,Hall D R, Opt Cnmmuu, 1985; 56:185
[3] Abrainski K M, Colly A D, Baker H J et al. A P L, 1989; 54:1833
[4] Francis G.Ionization phenomena in gases. New York:Academic Press Inc, 1960:81.172