1. Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Am Mühlenberg 1, DE-14476 Potsdam, Germany
2. Institute of Radiation Problems ANAS, B.Vahabzade 9, AZ1143 Baku, Azerbaijan
3. Department of Mathematics, Khazar University, Mehseti St. 41, AZ1096 Baku, Azerbaijan
4. Department of Physics, Bogazici University, 34342 Bebek, Istanbul, Turkey
5. General Relativity Department, Institute of Physics, Kazan Federal University, Kremlevskaya 16a, 420111 Kazan, Russia
6. Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudny 141700, Russia