J. Jahnke, W. Schäfer, and A. Zündorf. Proc. European Software Engineering Conf. (ESEC), volume 1013 of Lecture Notes in Computer Science, page 193--210. Springer-Verlag, (1997)
P. Naur, and B. Randell (Eds.).
. Brussels, Scientific Affairs Division, NATO, (1969)Report of a conference sponsored by the NATO Science Committee,
Garmisch, Germany, 7th to 11th October 1968.
J. Goguen. Proc. Conf. Discrete Mathematics and Theoretical Computer Science, volume 21 of Australian Computer Science Communications, page 35--59. Springer-Verlag, (1999)