PHYSICAL REVIEW B, vol. 76, no. 3, page. 35110 - 35110, 2007-07
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 53, no. 6, page. 3640 - 3644, 2008-12
NATURE PHYSICS, vol. 4, no. 3, page. 205 - 209, 2008-03