1. Department of Applied Mathematics and the Institute of Natural Sciences, Kyung Hee University, Yongin, Republic of Korea
2. SDU Robotics, Maersk Mc-Kinney Moller Institute, University of Southern Denmark, Odense, Denmark
3. Department of Mathematics, University of Seoul, Dongdaemun, Republic of Korea
4. Department of Mathematics, Kunsan National University, Gunsan, Republic of Korea