P. Mayr, A. Scharnhorst, B. Larsen, P. Schaer, and P. Mutschke. Proceedings of the 36th International European Conference on Information Retrieval, ECIR'14, April 13 - April 16, 2014, Amsterdam, The Netherlands, volume 8416 of Lecture Note in Computer Science, page 798–801. Springer, (2014)