S. Easterbrook, E. Yu, J. Aranda, Y. Fan, J. Horkoff, M. Leica, and R. Qadir. RE '05: Proceedings of the 13th IEEE International Conference on Requirements Engineering (RE'05), page 199--208. Washington, DC, USA, IEEE Computer Society, (2005)
B. Nuseibeh, J. Kramer, and A. Finkelstein. ICSE '93: Proceedings of the 15th international conference on Software Engineering, page 187--196. Los Alamitos, CA, USA, IEEE Computer Society Press, (1993)