M. Maguire, and N. Bevan. Proceedings of the IFIP 17th World Computer Congress - TC13 Stream on Usability: Gaining a Competitive Edge, page 133--148. Deventer, The Netherlands, The Netherlands, Kluwer, B.V., (2002)
A. Sutcliffe. Proceedings of the 11th IEEE International Conference on Requirements Engineering, page 320--. Washington, DC, USA, IEEE Computer Society, (2003)