1. Game Software, School of Games, Hongik University, Building B, Room No. 211, 2639 Sejong-ro, Jochiwon-eup, Chungcheongnam-do 339-701, Republic of Korea
2. Department of Multimedia Science, Sookmyung Women's University, Cheongpa-ro 47-gil 100, Yongsan-gu, Seoul 140-742, Republic of Korea
3. Division of IT Engineering, Korea Maritime and Ocean University, 727 Taejeong-ro, Yeongdo-gu, Busan 606-791, Republic of Korea