DISCRETE MATHEMATICS, vol. 238, no. 1-3, page. 67 - 80, 2001-07-28
IEEE TRANSACTIONS ON INFORMATION THEORY, vol. 47, no. 4, page. 1638 - 1644, 2001-05
DISCRETE MATHEMATICS, vol. 226, no. 1-3, page. 403 - 409, 2001-01-06