1. Department of Applied Mathematics and Cybernetics, Petrozavodsk State University, Lenin str. 33, 185910 Petrozavodsk, Russia
2. Institute of Applied Mathematical Research, Karelian Research Centre of Russian Academy of Sciences, Pushkinskaja str. 11, 185910 Petrozavodsk, Russia
3. Moscow Center for Fundamental and Applied Mathematics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, 119991 Moscow, Russia
4. Department of Information Engineering, University of Pisa, Via G. Caruso 16, 56122 Pisa, Italy