1. Davis, M.: Software Requirements: Objects, Functions, and States. Prentice Hall, Englewood Cliffs (1993)
2. Leffingwell, D.: Calculating the return on investment from more effective requirements management. American Programmer 10, 13–16 (1997)
3. CHAOS: Software Development Report by the Standish Group (1995),
http://www.standishgroup.com/chaos.html
4. Ibanez, M.: European user survey analysis. Tech. rep. ESI report TR95104. European Software Institute, Zamudio, Spain (1996),
www.esi.es
5. Davis, A., Jordan, K., Nakajima, T.: Elements underlying the specification of requirements. Ann. Softw. Eng. 3, 63–100 (1997)