International Workshop on Requirements Engineering : Foundations of Software Quality Heidelberg, Germany, Facultés universitaires Notre-Dame de la Paix (Namur, Belgium), Pohl, K., Dubois, E., & Opdahl, A. L. (1999). Proceedings of the Fifth International Workshop on Requirements Engineering: Foundations of Software Quality : REFSQ '99, Heidelberg, Germany, 14-15 June, 1999. Presses universitaires de Namur.

International Workshop on Requirements Engineering : Foundations of Software Quality Heidelberg, Germany, Belgium) Facultés universitaires Notre-Dame de la Paix (Namur, Klaus Pohl, Eric Dubois, and Andreas L. Opdahl. Proceedings of the Fifth International Workshop on Requirements Engineering: Foundations of Software Quality : REFSQ '99, Heidelberg, Germany, 14-15 June, 1999. Namur, Belgium: Presses universitaires de Namur, 1999.

International Workshop on Requirements Engineering : Foundations of Software Quality Heidelberg, Germany, et al. Proceedings of the Fifth International Workshop on Requirements Engineering: Foundations of Software Quality : REFSQ '99, Heidelberg, Germany, 14-15 June, 1999. Presses universitaires de Namur, 1999.