1. Istanbul Technical University, Ayazaga Campus, Faculty of Science and Letters, 34469 Maslak/Istanbul, Turkey
2. Dipartimento di Matematica, Università Statale di Bergamo, Piazza Rosate 2, Bergamo, Italy
3. Boğaziçi University, Kandilli Observatory and, Earthquake Research Institute, Çengelköy, Istanbul, Turkey