JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 29, no. 1, page. 9 - 16, 1996-02
PHYSICA D, vol. 89, no. 3-4, page. 315 - 328, 1996-01-01
PHYSICAL REVIEW B, vol. 53, no. 2, page. R502 - R505, 1996-01-01