Applied Mathematics. A Journal of Chinese Universities. Ser. B (Appl. Math. J. Chinese Univ. Ser. B) (20090101), 24, no.~1, 114-118. ISSN: 1005-1031 (print).eISSN: 1993-0445.
Applied Mathematics. A Journal of Chinese Universities. Ser. B (Appl. Math. J. Chinese Univ. Ser. B) (20080101), 23, no.~1, 65-68. ISSN: 1005-1031 (print).eISSN: 1993-0445.