M. Ageev, Q. Guo, D. Lagun, and E. Agichtein. Proceedings of the 34th international ACM SIGIR conference on Research and development in Information Retrieval, page 345--354. New York, NY, USA, ACM, (2011)
A. Quinn, and B. Bederson. Proceedings of the 2011 annual conference on Human factors in computing systems, page 1403--1412. New York, NY, USA, ACM, (2011)