JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 45, no. 4, page. 1045 - 1051, 2004-10
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 44, no. 5, page. 1265 - 1268, 2004-05
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 44, no. 5, page. 1269 - 1273, 2004-05