1. Department of Mathematics, Manipur University, Canchipur 795003, Manipur, India
2. Department of Basic Sciences and Humanities, Manipur Institute of Technology, A Constituent College of Manipur University, Takyelpat 795004, Manipur, India
3. Department of Mathematics and Applied Mathematics, Sefako Makgatho Health Sciences University, Ga-Rankuwa 0208, South Africa
4. Department of Architecture, Federico II Naples University, Via Toledo 402, 80134 Naples, Italy