1. School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
2. Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais, Brazil
3. School of Education, Can Tho University, Campus II, 3/2 Street, Xuan Khanh, Ninh Kieu, Can Tho City, Vietnam
4. College of Science, Technology and Engineering, James Cook University, Townsville, Australia
5. Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia