1. School of Applied Science, Netaji Subhas Institute of Technology, Azad Hind Fauj Marg, Sector-3, Dwarka, New Delhi 110 045, India
2. Fachbereich MND, Fachhochschule Giessen-Friedberg, University of Applied Sciences, Wilhelm-Leuschner-Straβe 13, Friedberg 61169, Germany
3. Department of Mathematics, Technical University of Cluj-Napoca, Cluj-Napoca 400020, Romania