Affiliation: | a Institute of Mathematics at the NAS, Kyiv, Ukraine b Department of Applied Mathematics, Agrarian University of Kraków, Poland;c V.A. Steklov Mathematical Institute of RAS, Moscow, Russian Federation d Abdus Salam International Centre of Theoretical Physics, Trieste, Italy;e AGH University of Science and Technology Department of Mining Geodesy, Kraków 30059, Poland f Ivan Franko State Pedagogical University, Drohobych, Lviv region, Ukraine; Department of Mechanics and Mathematics T. Shevchenko National University, Kyiv, Ukraine |