1. D. Ivanenko (Ed.), Nonlinear Quantum Field Theory, Inostrannaia Literatura, 1959.
2. V.G. Makhankov, Phys. Rep. 35 (1971) 1.
3. R. Rajaraman, Solitons and Instantions, North-Holland, Amsterdam, The Netherlands, 1982.
4. A.O. Barut, Geom. Algebr. Aspects Nonlinear Field Theory 37 (1989).
5. W.I. Fushchych, W.M. Shtelen, N.I. Serov, Symmetry Analysis and Exact Solution of Nonlinear Equations of Mathematical Physics, Naukova Dumka, Kiev, 1989.