1. Costello RJ, Liu DB (1995) Metrics for requirement. Eng J Syst Softw 29:39–63. Elsevier Science, North Holland, pp 39–63
2. The Standish group research for staggering bugs and effort, http://standishgroup.com
3. IEEE Computer Society (1998) IEEE recommended practice for software requirement specifications. IEEE Inc, NY, pp 1–37
4. Mc Cabe TJ (1976) A complexity measure. IEEE Trans Softw Eng SE-2(4), pp 308–320
5. Chaudhary BD, Sahasrabuddne HV (1980) Meaningfulness as a factor of program complexity ACM transaction ACM – 0-89791-028-1/80/1000/0457, pp 457–466