1. The Polytechnic, Department of Organic Chemistry, Splaiul Independentei 313, 76026 Bucharest, Roumania
2. The Polytechnic, Departm ent of Organic Chemistry, Splaiul Independentei 313, 76026 Bucharest, Roumania
3. I. P. S. O. I. Centre Universitaire Saint-Jérôme, Rue Henri Poincaré, 13013 Marseille, France