1. Da Vinci College of General Education, Chung-Ang University, General Education Building, 84 HeukSeok-Ro, DongJak-Gu, Seoul 06974, Korea
2. Department of Mathematics Education, Hongik University, 94 Wausan-ro, Mapo-gu, Seoul 04066, Korea
3. Sobolev Institute of Mathematics, pr. Kotyuga 4, Novosibirsk 630090, Russia
4. Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
5. School of Engineering, Computer and Mathematical Sciences, Auckland University of Technology, AUT Tower, 2-14 Wakefield Street, Auckland 1010, New Zealand