1. Rosner J. Phys. Rev. Lett., 21, 950 (1968)
2. Jacob M. and Weyers J., Nuovo Cimento, 69B, 521 (1970)
3. Balitzky Ya. Ya. et al., Yad. Fiz., 35, 1300 (1982)
4. Amirzadeh J. et al., Phys. Lett., 89B, 125 (1979)
5. Grigoryan A.A. and Kaidaiov A.B, Pis’ma Zh. Eksp. Teor. Fiz., 28, 318 (1978); Yad., Fiz., 32, 540 (1980)