1. Centre of Mathematics, Fundamental Applications and Operations Research (CMAFCIO), Universidade de Lisboa, Portugal; and Lavrentyev Institute of Hydrodynamics, SB RAS, Novosibirsk, Russia
2. CMAFCIO, Universidade de Lisboa, Portugal; and Departmento de Matemática, Faculdade de Ciências e Tecnologia, Universidade do Algarve, Faro, Portugal
3. Department of Mechanics and Mathematics, Al-Farabi Kazakh National University, Almaty, Kazakhstan