T. Moon, A. Smola, Y. Chang, and Z. Zheng. Proceedings of the third ACM international conference on Web search and data mining, page 151--160. New York, NY, USA, ACM, (2010)
L. Rigutini, T. Papini, M. Maggini, and M. Bianchini. Proceedings of the 18th international conference on Artificial Neural Networks, Part II, page 899--908. Berlin, Heidelberg, Springer-Verlag, (2008)