P. Berkhin, J. Beche, and D. Randall. Proceedings of the seventh ACM SIGKDD international conference on Knowledge discovery and data mining, page 414--419. ACM, (2001)
K. Lamm, T. Mandl, and R. Koellex. Proceedings of the 10th cross-language evaluation forum conference on Multilingual information access evaluation: text retrieval experiments, page 538--543. Berlin, Heidelberg, Springer-Verlag, (2009)