1. Dipartimento di Matematica e Geoscienze, Università di Trieste, Italy. E-mails: alessang@units.it, esincich@units.it
2. Departments of Computational and Applied Mathematics, Earth Science, Rice University, Houston, Texas, USA. E-mail: mdehoop@rice.edu
3. Department of Mathematics and Statistics, University of Limerick, Ireland. E-mail: romina.gaburro@ul.ie