1. Corliss, C.H., Bozman, W.E.: N.B.S. Monograph53 (1962)
2. Garpman, S., Lid�, G., Rydberg, S., Svanberg, S.: Z. Phys.247, 238 (1971)
3. L'vov, B.V.: Dr. Sc. Thesis, Leningrad State University 1972
4. Dynefors, B.I.: Phys. Scr.11, 375 (1975)
5. Muradov, V.G., Fomichev, V.M.: Zh. Prikl. Spektrosk.27, 980 (1977)