1. Bias, R.G., Karat, M.-C.: Justifying cost-justifying usability. In: Bias, R.G., Mayhew, D.J. (eds.) Cost-Justifying Usability, pp. 1–16. Morgan Kaufmann, San Francisco (2005)
2. Marcus, A.: User Interface Design’s Return on Investment. In: Bias, R.G., Mayhew, D.J. (eds.) Cost-Justifying Usability, pp. 17–39. Morgan Kaufmann, San Francisco (2005)
3. Zowghi, D., da Rimini, F., Bano, M.: Problems and challenges of user involvement in software development. In: EASE 2015, pp. 1–10. ACM, New York (2015)
4. Haberfellner, R., de Weck, O., Fricke, E., Vössner, S.: Systems Engineering: Grundlagen und Anwendung. Orell Füssli Verlag, Zürich (2018)
5. International Organization for Standardization: ISO/IEC TR 25060:2010-07, System und Software-Engineering. Beuth, Berlin (2010)