1. National Institute for Research and Development of Isotopic and Molecular Technologies, P.O. Box 700, R-3400 Cluj-Napoca 5, Romania
2. Laboratory of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
3. Universidad Nacional de Educación a Distancia, Departamento de Ciencias y Tecnicas Fίsico Quimicas, Senda del Rey 9, 28040 Madrid, Spain