1. A. Galperin, E. Ivanov, V. Ogievetsky, and E. Sokatchev, JETP Lett.
40 (1984) 155
2. A. Galperin, E. Ivanov, S. Kalitzin, V. Ogievetsky, and E. Sokatchev, Class. Quant. Grav.
1 (1984) 469.
3. V. I. Ogievetsky and I. V. Polubarinov, Yad. Fiz.
4 (1966) 216.
4. Ch. Devchand and V. Ogievetsky, Nucl. Phys.
B481 (1996) 188.
5. M. A. Vasiliev, Phys. Lett.
B285 (1992) 225