PHYSICAL REVIEW B, vol. 54, no. 1, page. 33 - 36, 1996-07-01
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 29, no. 5, page. 609 - 613, 1996-10
PHYSICA STATUS SOLIDI B-BASIC RESEARCH, vol. 208, no. 1, page. 129 - 135, 1998-07
JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL, vol. 34, no. 46, page. 9793 - 9801, 2001-11-23
PHYSICAL REVIEW B, vol. 66, no. 7, 2002-08-15