Affiliation: | (1) Department of Mathematical Analysis, Ghent University, Building S-22, Galglaan 2, B-9000 Ghent, Belgium;(2) Departamento de Matemática, Universidade de Trás-os-Montes e Alto Douro, P-5000-911 Vila Real, Portugal;(3) Department of Mathematics, Section of Analysis, Katholieke Universiteit Leuven, Celestijnenlaan 200-B, B-3001 Leuven, Belgium |