G. Groh, and C. Ehmig. GROUP '07: Proceedings of the 2007 international ACM conference on Supporting group work, page 127--136. New York, NY, USA, ACM, (2007)
D. Morris, M. Morris, and G. Venolia. CHI '08: Proceeding of the twenty-sixth annual SIGCHI conference on Human factors in computing systems, page 1207--1216. New York, NY, USA, ACM, (2008)
G. Xue, H. Zeng, Z. Chen, W. Ma, H. Zhang, and C. Lu. SIGIR '03: Proceedings of the 26th annual international ACM SIGIR conference on Research and development in informaion retrieval, page 56--63. New York, NY, USA, ACM, (2003)