JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 55, no. 6, page. 2460 - 2464, 2009-12
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 53, no. 6, page. 3671 - 3674, 2008-12
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 51, no. 1, page. 130 - 134, 2007-07