Mikhail M. Lavrent'ev โ ; Alexander A. Avdeev, Institute of Computational Modeling, Russian Academy of Sciences, Krasnoyarsk, Russia; Mikhail M. Lavrent'ev (Jn.), Sobolev Institute of Mathematics, Russian Academy of Sciences, Novosibirsk, Russia; Viatcheslav I. Priimenko, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil.