JOURNAL OF PURE AND APPLIED ALGEBRA, vol. 140, no. 2, page. 125 - 135, 1999-07-28
JOURNAL OF PURE AND APPLIED ALGEBRA, vol. 140, no. 2, page. 107 - 124, 1999-07-28
COMMENT. MATH. UNIV. ST. PAUL, vol. 48, no. 1, page. 19 - 24, 1999-07
JOURNAL OF ALGEBRA, vol. 216, no. 2, page. 481 - 510, 1999-06-15