Acknowledgements.

I am grateful to Th. M. Liebling who provided me with an ideal opportunity to visit EPFL for the academic year 1993-1994. Without his support, the present form of this program would not have existed. There are many people who helped me to improve cdd, in particular, I am indebted to David Avis, Alain Prodon, Francois Margot, Henry Crapo, Alexander Bockmayr, David Bremner, Matthew Saltzman, Ewgenij Gawrilow and Michael Joswig.

Finally, I would like to thank both H.-J. Lüthi (ETHZ) and Th. M. Liebling (EPFL) for their continuing support for the current new development (cdd+, cddlib).