Giovanni Bellettini

University of Siena
Department of Information Engineering and Mathematical Sciences
via Roma 56, 53100 Siena, Italy

International Centre for Theoretical Physics, Mathematics Section
Strada Costiera 11, I-34151 Trieste, Italy

E-Mail: bellettini@diism.unisi.it

Shokhrukh Kholmatov

University of Vienna
Faculty of Mathematics
Oskar-Morgenstern-Platz 1, 1090 Vienna, Austria

E-Mail: shokhrukh.kholmatov@univie.ac.at

Paolo Piovano

Polytechnic University of Milan
Department of Mathematics
Piazza Leonardo da Vinci 32, 20133 Milan, Italy

E-Mail: paolo.piovano@polimi.it