1. Faculty of Chemistry and Pharmacy, Sofia University “St. Kliment Ohridski”, 1 J. Bourchier Ave., 1164 Sofia, Bulgaria
2. Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
3. Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
4. Institute of Polymers, Bulgarian Academy of Sciences, Akad. G. Bonchev St., Bl 103A, 1113 Sofia, Bulgaria