JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 41, no. 3, page. 314 - 321, 2002-09
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 40, no. 2, page. 232 - 236, 2002-02
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 38, no. 1, page. 14 - 18, 2001-01