1. ICEx-UFMG, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
2. Laboratoire Paul Painlevé UMR 8524, Université de Lille CNRS, Lille, France
3. Department of Mathematics, HCMC University of Pedagogy, Ho Chi Minh, Vietnam
4. Department of Mathematics, Heriot-Watt University, Edinburgh, UK
5. The Maxwell Institute for the Mathematical Sciences, Edinburgh, UK