1. Department of Mathematics, Statistics, and Computer Sciencies–InaMat2, Universidad Pública de Navarra, Campus de Arrosadía, Pamplona, 31006 Spain
2. Department of Mathematics and Computer Sciences, Universidad de La Rioja, Logroño, 26004 Spain
3. Faculty of Mathematics and Physics, Department of Mathematical Analysis, Charles University, Sokolovská 83, 186 75 Praha 8, Czech Republic
4. Institute of Mathematics, Czech Academy of Sciences, Žitná 25, 115 67 Praha 1, Czech Republic