1. Department of Mathematics, D.S.B. Campus Kumaun University Nainital Uttarakhand India
2. Department of Mathematics Faculty of Science Maejo University Thailand
3. UNNE, Fa CENA, Corrientes Argentina and UTN‐FRRE Resistencia Chaco Argentina
4. Department of Mathematics P. C. Vigyan Mahavidyalaya Jai Prakash University Chapra India