1. Department of Mathematics, Netaji Subhas University of Technology, New Delhi 110078, India
2. Department of Mathematical Sciences, Indian Institute of Technology (BHU), Varanasi 221005, India
3. UFCG-Universidade Federal de Campina, Grande-Unidade, Academica de Fisica, 58429-900 Campina Grande, PB, Brazil
4. PPGCosmo, CCE, Universidade Federal do Espírito Santo (UFES), 29.075-910, Vitria, ES, Brazil