M. Kompan, and M. Bieliková. E-Commerce and Web Technologies, volume 61 of Lecture Notes in Business Information Processing, Springer Berlin Heidelberg, (2010)
R. Pon, A. Cardenas, D. Buttler, and T. Critchlow. Proceedings of the 13th ACM SIGKDD international conference on Knowledge discovery and data mining, page 560--569. New York, NY, USA, ACM, (2007)