1. Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia
2. LERMA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, 5 Place Jules Janssen, 92190 Meudon, France
3. Institute Isaac Newton of Chile, Yugoslavia Branch, 11060 Belgrade, Serbia
4. Department of Applied Physics, Technical University-Sofia, 1000 Sofia, Bulgaria