1. Balser, M. (1997). Wiederverwendung von Beweisen nach Modifikation. Diplomarbeit, Fakultät für Informatik, Universität Ulm, Germany. (in German).
2. Bertot, J. and Bertot, Y. (1996). Ctcoq: a system presentation. In 13th International Conference on Automated Deduction, CADE-13,Springer LNCS.
3. Boyer, R. S. and Moore, J. S. (1979). A Computational Logic. Academic Press, New York.
4. Broy, M., Facchi, C., Grosu, R., Hettler, R., HuBmann, H., Nazareth, D., Regensburger, F., Slotosch, O., and Stolen, K. (1993). The Requirements and Design Specification Language SPECTRUM. An informal introduction. Version 1.0. Part 1/II. Technical Report TUM-19311 and 19312, Technische Universität München, Fakultät für Informatik, TUM, 80290 München, Germany.
5. Constable, R. L., Allen, S. E, Bromley, H. M., Cleaveland, W. R., Cremer, J. F, Harper, R. W., Howe, D. J., Knoblock, T. B., Mendler, N. P., Panagaden, P., Sasaki, J. T., and Smith, S. F. (1986). Implementing Mathematics with the Nuprl Proof Development System. Prentice Hall.