A. Maclean, R. Young, and T. Moran. CHI '89: Proceedings of the SIGCHI conference on Human factors in computing systems, page 247--252. New York, NY, USA, ACM Press, (1989)
R. Keller, and R. Schauer. Proceedings of the 1998 International Conference on Software
Engineering, page 302--311. IEEE Computer Society Press / ACM Press, (1998)
A. Rose, B. Shneiderman, and C. Plaisant. ACM Proc. of DIS 95, Symposium on Designing Interactive Systems: Processes, Practices, Methods & Techniques, page 115-122. (August 1995)