Je tiens egalement a remercier l'editeur KLUWER que nous a garanti une pu- blication aisee et attrayante. Ce n'est pas sans fierte que j'ai l'honneur d'introduire la presente edition des actes du congres. PREFACE In the text mentioned above, it has been stated that the texts of the General Rap- porteurs were published in their original language and the texts of the opening and closing speeches, although they were made in the five Congress languages (Dutch, French, English, German and Spanish), were published in English, as the Belgian organisers deemed this to be the most rational solution,...