1. K.A. Gorshkov, L.A. Ostrovsky, V.V. Papko, Interactions and bound states of solitons as classical particles. Zh. Eksp. Teor. Fiz. 71(2), 585–593 (1976) (in Russian. Engl. transl.: Sov. Phys. JETP. 44(2), 306–311, 1976)
2. V.I. Karpman, E.M. Maslov, Perturbation theory for solitons. Zh. Eksp. Teor. Fiz. 73, 537–559 (1977) (in Russian. Engl. transl.: Sov. Phys. JETP. 46, 281–295, 1977)
3. D.J. Kaup, A.С. Newell, Soliton as particles, oscillator and in slowly changing media: a singular perturbation theory. Proc. R. Soc. London A 301(1701), 413–446 (1978)
4. J.P. Keener, D.W. McLaughlin, Soliton under perturbation. Phys. Rev. A 16, 777–790 (1977)
5. N.J. Zabusky, M.D. Kruskal, Interaction of “solitons” in a collisionless plasma and the recurrence of initial states. Phys. Rev. Lett. 15(6), 240–243 (1965)