JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 53, no. 6, page. 3667 - 3670, 2008-12
PHYSICAL REVIEW LETTERS, vol. 88, no. 19, 2002-05-13
SURFACE SCIENCE, vol. 385, no. 2-3, page. L978 - L983, 1997-08-10
PHYSICAL REVIEW B, vol. 47, no. 20, page. 13594 - 13598, 1993-05-15