1. a Institute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences , H-1525, Budapest, P.O. Box 17, Hungary
2. b Institute of Chemistry, University of Novi Sad , Trg D. Obradovica, 3, 21000, Novi Sad, Yugoslavia
3. c University of Belgrade, Faculty of Chemistry , Studentski trg 16, P.O. Box 550, 11000, Belgrade, Yugoslavia