Proceedings of the XII Serbian-Bulgarian Astronomical Conference (XII SBAC) Sokobanja, Serbia, September 25-29, 2020 Editors: L. Č. Popović, V. A. Srećković, M. S. Dimitrijević and A. Kovačević Publ. Astron. Soc. “Rudjer Bošković” No 20, 2020, 33-38