1. V.S. Lisitsa, Opt. Spectrosc. 31, 468 (1971)
2. Yu.N. Demkov, B.S. Monozon, V.N. Ostrovsky, Sov. Phys. JETP 30, 775 (1970)
3. V. Fock, Z. Physik 98, 145 (1935)
4. V.S. Lisita, G.V. Sholin, Sov. Phys. JETP 34, 484 (1972)
5. R.L. Greene, J. Cooper, E.W. Smith, J. Quant, Spectrosc. Rad. Transf. 15, 1025 (1975)