1. Chair of Computational Mathematics, Fundación Deusto, University of Deusto, 48007 Bilbao, Basque Country, Spain
2. Chair in Applied Analysis, Alexander von Humboldt-Professorship, Department of Mathematics, Friedrich-Alexander-Universität, Erlangen-Nürnberg, 91058 Erlangen, Germany
3. Departamento de Matemáticas, Universidad Autónoma de Madrid, 28049 Madrid, Spain