1. J. S. Russell, Report on Waves, British Ass. Reports 1844, see also R. K. Bullough and P. J. Chaudrey in: Solitons, ed. by R. K. Bullough and P. J. Chaudrey, Springer, 1980.
2. D. J. Korteweg and G. de Vries, Phil. Mag. 39, 422 (1895).
3. A. Seeger, Solitons in Crystals, Proc. 3rd Int. Symp. on Cont. Models of Discrete Cryst., Freudenstadt, ed. by E. Kröner and K. H. Antony, Univ. Waterloo, Ontario, 253 (1980).
4. see, e.g. Solitons, ed. by R. K. Bullough and P. J. Chaudrey, Springer, 1980, Solitons and Condensed Matter Physics, ed. by A. R. Bishop and T. Schneider, springer, 1978, G. Eilenberger, Solitons, Springer, 1981.
5. P. Bak, Rep. Prog. Phys. 45, 587 (1982). For a recent development, see E. Allroth and H. Müller-Krumbhaar, to be published.