1. Sumy State University, 2, Rymskogo-Korsakova St., 40007 Sumy, Ukraine
2. Poznan University of Technology, 5, M. Skłodowskiej-Curie Sq., 60-965 Poznan, Poland
3. Sumy State Pedagogical University named after A. S. Makarenko, 87, Romenska St., 40002 Sumy, Ukraine