PHYSICA B-CONDENSED MATTER, vol. 312, page. 673 - 674, 2002-03
PHYSICAL REVIEW LETTERS, vol. 93, no. 7, 2004-08-13
PHYSICAL REVIEW B, vol. 74, no. 16, 2006-10
PHYSICAL REVIEW LETTERS, vol. 90, no. 18, 2003-05-09