Elena Akhmatskaya -
Fujitsu Laboratories of Europe Ltd (FLE), Hayes Park Central, Hayes End Road, Hayes UB4 8FE, United Kingdom
Nawaf Bou-Rabee -
Department of Mathematics, Freie Universität Berlin, Arnimallee 2-6, 14195 Berlin, Germany
Sebastian Reich -
Universität Potsdam, Institut für Mathematik, Am Neuen Palais 10, D-14469 Potsdam, Germany