MATHEMATICAL RESEARCH LETTERS, vol. 17, no. 4, page. 625 - 636, 2010-07
MATHEMATICAL RESEARCH LETTERS, vol. 17, no. 4, page. 721 - 729, 2010-07
MATHEMATISCHE ZEITSCHRIFT, vol. 264, no. 2, page. 317 - 326, 2010-02
JOURNAL OF THE KOREAN MATHEMATICAL SOCIETY, vol. 47, no. 1, page. 41 - 62, 2010-01