P. Zigoris, and Y. Zhang. Proceedings of the 15th ACM international conference on Information
and knowledge management (CIKM-2006), page 397--404. (2006)
L. Zhang, J. Barnden, R. Hendley, and A. Wallington. Proceedings of the Workshop on Sentiment and Subjectivity in Text, page 47--54. Sydney, Australia, Association for Computational Linguistics, (July 2006)