1. St. Kliment Ohridski University of Sofia; Faculty of Chemistry and Pharmacy; 1, James Bourchier av. 1164 Sofia Bulgaria
2. Department of Materials Science and Engineering; University of Florida; 1180 Center Drive Gainesville Florida 32611 USA
3. Institute of Pharmaceutical Chemistry; University of Szeged; H-6720 Szeged Eötvös u. 6. Hungary