Nonlinear wave motion : complexity and simplicity revisitedEngelbrecht, Jüri; Salupere, Andrus; Peterson, PearuAbstracts of IUTAM/IFToMM Symposium on Synthesis of Nonlinear Dynamical Systems, Riga, Latvia, 24-28 Aug. 19981998 / p. 3-4 https://link.springer.com/chapter/10.1007/978-94-011-4229-8_3