1. Austin, S., & Parkin G.I. (1993).Formal methods: A survey report. The National Physical Lab. Middlesex.
2. Balzer, R., & Goldman, N. (1979). Principles of good software specification and their implications for specification languages.Proceedings of IEEE Conference on Specifications of Reliable Software, 58–67.
3. Barden, R., Stepney, S., & Cooper, D. (1994).Z in practice. Hertfordshire, UK: Prentice Hall.
4. Basili, V.R. (1980). Tutorial on models and metrics for software management and engineeering.IEEE Catalog No. EH0-167-7. IEEE Computer Society. Los Alamitos, CA.
5. Basili, V.R., Selby, R.W. Jr., & Philips, T. (1983). Metric analysis and validation across Fortran projects.IEEE Transaction Software Engineerng SE-9, 652–663.