JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 30, no. 2, page. 214 - 220, 1997-04
MODERN PHYSICS LETTERS B, vol. 10, no. 9, page. 401 - 407, 1996-04-20
INTERNATIONAL JOURNAL OF MODERN PHYSICS B, vol. 10, no. 6, page. 701 - 712, 1996-03-15