JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 54, no. 2, page. 712 - 715, 2009-02
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 53, no. 2, page. 1084 - 1088, 2008-08
PHYSICAL REVIEW LETTERS, vol. 90, no. 18, 2003-05-09
PHYSICAL REVIEW B, vol. 64, no. 24, 2001-12-15
PHYSICAL REVIEW B, vol. 61, no. 17, page. 11506 - 11509, 2000-05-01