1. ETSID, Departamento de Matemática Aplicada & CITG, Universitat Politècnica de València, 46022 Valencia, Spain
2. Department of Mathematics, University of Kalyani, Kalyani, District Nadia, West Bengal 741235, India
3. Rajbari, Rabindrapalli, R. N. Tagore Road, P.O.-Krishnagar, District Nadia, West Bengal 741101, India
4. Dhulauri Rabindra Vidyaniketan (H.S.), Vill +P.O. Dhulauri, P.S. Domkal, District Murshidabad, West Bengal 742308, India