1. Nonlinear Analysis and Applied Mathematics Research Group (NAAM), Department of Mathematics, Faculty of Sciences; King Abdulaziz University; PO Box 80203 Jeddah 21589 Saudi Arabia
2. Department of Mathematics; Tallinn University of Technology; Tallinn 19068 Estonia
3. Laboratoire de Mathématiques, Pôle Sciences et Technologies; Université de La Rochelle; Avenue Michel Crépeau La Rochelle Cedex 17042 France
4. RICAM; Austrian Academy of Sciences; Altenbergerstrasse 69 Linz A-4040 Austria