1. Gilmore, P., Catastrophe Theory for Scientists and Engineers, New York: Wiley, 1980.
2. Rakhimov, A.Kh., St. Petersb. Math. J., 1993, vol. 27, no. 1, p. 39.
3. Rakhimov, A.Kh., Funct. Anal. Appl., 1993, vol. 27, no. 4, p. 813.
4. Kudashev, V.R. and Suleimanov, B.I., JETP Lett., 1995, vol. 62, no. 4, p. 382.
5. Kudashev, V.R. and Suleimanov, B.I., J. Appl. Math. Mech., 2001, vol. 65, no. 3, p. 441.