1. Space Research Center, Department of Astronomy and Astrophysics, School of Natural Sciences and Medicine, Ilia State University, Cholokashvili Av. 3/5, Tbilisi 0162, Georgia
2. E. Kharadze National Astrophysical Observatory, Deapartment of Galaxies and Stars, Mt. Kanobili, Abastumani 0803, Georgia
3. Instituto National di Astrofizica e Fizica spatiale, Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy