1. Department of Mathematical Methods in Economy, Far Eastern Federal University, Vladivostok, Russia + Hanrimwon, Kwangwoon University ,Seoul, Republic of Korea
2. Department of Mathematics, Sogang University, Seoul, Republic of Korea
3. Department of Mathematics, Kwangwoon University, Seoul, Republic of Korea
4. Department of Mathematics Education and ERI, Gyeongsang National University, Jinju, Republic of Korea