1. R. K. Dodd, G. Eilenberger, G. Gibbon, and H. Morris, Solitons and Nonlinear Wave Equations (Academic, New York, 1982; Mir, Moscow, 1988).
2. A. C. Newel, Solitons in Mathematics and Physics (Society for Industrial and Applied Mathematics, Philadelphia, Pa., 1985; Mir, Moscow, 1989), p. 386.
3. Modern Crystallography. Structure of Crystals, Ed. by B. K. Vainshtein, V. M. Fridkin, and V. L. Indenbom (Nauka, Moscow, 1979), Vol. 4, p. 360.
4. V. L. Indenbom, Kristallografiya 3, 197 (1958).
5. G. N. Dubnova and V. L. Indenbom, Kristallografiya 11, 642 (1996) [Crystallogr. Rep. 11, 554 (1996)].