1. Faculty of Mathematics and Information Science Warsaw University of Technology Warsaw Poland
2. Alexandru Ioan Cuza University of Iaşi, Department of Mathematics Iaşi Romania
3. Octav Mayer Institute of Mathematics of the Romanian Academy Iaşi Romania
4. Head of Lehrstuhl für Nichtlineare Analysis und Modellierung, Fakultät für Mathematik Universität Duisburg‐Essen, Campus Essen Essen Germany