Acknowledgment

The authors wish to thank all the researchers of the HUDEM project without whom it was impossible to write this paper. In spite of the difficult current international situation, it was possible for our foreign researchers to find the necessary ressources for providing an excellent work and for maintaining an enthousiastic spirit of collaboration. They think particularly to N. Milisavljevic, A. Pizurica and D. Milojevic. They also wish to emphasize the excellent work performed by the Belgian researchers, A. Engelbeen, M. Storme, B. Scheers, L. van Kempen and B. Weetjens. They also wish to thank Prof I. Lemahieu, Prof. W. Philips, Prof. P. Van Ham, Prof. J.A.S. Smith, Prof. Van Hecke, Prof. A. Vander Vorst and Prof. J. Cornelis for the support they provide to the researchers.