N. Liu, and Q. Yang. Proceedings of the 31st annual international ACM SIGIR conference on Research and development in information retrieval, page 83--90. New York, NY, USA, ACM, (2008)
O. Streibel, and R. Alnemr. Proceedings of the 3rd international workshop on Search and mining user-generated contents, page 3--10. New York, NY, USA, ACM, (2011)