1. b Dept. de Quimica , College Universitari de Girona. U.A.B , Pça. Hospital 6, Girona, (Spain)
2. c Quimica Analitica. Universitat Autònoma de Barcelona , Bellaterra, (Spain)
3. a Dept. of Inorganic Chemistry , Royal Institute of Technology (KTH) , Stockholm, S-100 44, (Sweden)