E. Chi, P. Pirolli, K. Chen, and J. Pitkow. Proceedings of the ACM CHI 2001
Conference on Human Factors in Computing Systems, page 490--497. Amsterdam: ACM Press, (2001)
E. Chi, P. Pirolli, and J. Pitkow. Proceedings of the ACM CHI 2000
Conference on Human Factors in Computing Systems, page 161--168. Amsterdam: ACM Press., (2000)