1. a Sektion Chemie , Martin-Luther-Universität , DDR-4020, Halle, German Democratic Republic
2. b Department of Chemistry , Univesity of Jammu , Jammu-Tawi, 180001, India
3. c VEB Spezialchemie , Abt. FE DDR-7143 Leipzing-Luützschena, Elsteraue 9, German Democratic Republic