PHYSICAL REVIEW LETTERS, vol. 91, no. 25, 2003-12-19
APPLIED PHYSICS LETTERS, vol. 83, no. 5, page. 920 - 922, 2003-08-04
PHYSICAL REVIEW LETTERS, vol. 90, no. 18, 2003-05-09
PHYSICAL REVIEW LETTERS, vol. 90, no. 1, 2003-01-10