[1] Univ Peloponnese, Dept Business Adm, GR- 24100 Kalamata, Greece
[2] Univ Thessaly, Dept Comp Sci & Biomed Informat, GR- 35100 Lamia, Greece
[3] Univ Edinburgh, Usher Inst, Edinburgh Med Sch, Edinburgh EH8 9YL, Scotland
[4] Univ Edinburgh, Sch Math, Edinburgh EH8 9YL, Scotland
[5] Alan Turing Inst, London NW1 2DB, England