1. Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII, 1, 28040-Madrid, Spain
2. International Center for Mechanical Sciences (CISM), Palazzo del Torso, Piazza Garibaldi, 33100-Udine, Italy
3. Institut für Physik, Humboldt-Universität Berlin, Newtonstraβe 15, 12489-Berlin, Germany
4. Faculty of Nonlinear Processes, N. G. Chernychevsky State University, Astrakhanskaya 83, 410012-Saratov, Russia