1. Department of Mathematics and Computer Science University of the Balearic Islands Cra. de Valldemossa, km 7.5 E-07122 Palma de Mallorca Spain
2. Institute of Digital Business Johannes Kepler University Linz Altenberger Strasse 69 4040 Linz Austria
3. Faculty of Technical Sciences University of Novi Sad Trg Dositeja Obradovica 6 21000 Novi Sad Serbia