PHYSICAL REVIEW B, vol. 80, no. 23, page. 235312 - 235312, 2009-12
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 53, no. 2, page. 986 - 989, 2008-08
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 51, no. 1, page. 130 - 134, 2007-07