Methodical requirements for training materials of on-line courses on the platform “Higher school mathematics teacher”Kateryna Vlasenko, Olena Chumak, Iryna Lovianova, Daria Kovalenko and Nataliia VolkovaE3S Web Conf., 166 (2020) 10011DOI: https://doi.org/10.1051/e3sconf/202016610011