I. Kulev, E. Janevska, M. Jovanovik, and D. Trajanov. Proceedings of the 8th International Conference for Informatics and Information Technology (CIIT 2011), page 43--47. Institute of Informatics, Skopje, Macedonia, (2011)
R. Wetzker, T. Alpcan, C. Bauckhage, W. Umbrath, and S. Albayrak. WI '07: Proceedings of the IEEE/WIC/ACM International Conference on Web Intelligence, page 482--486. Washington, DC, USA, IEEE Computer Society, (2007)