1. Department of General and Inorganic Chemistry with Methodology of Chemistry Education, Faculty of Chemistry, University of Plovdiv, “Tzar Assen” Str. 24, 4000 Plovdiv, Bulgaria
2. Department of Organic Chemistry and Pharmacognosy, Faculty of Chemistry and Pharmacy, University of Sofia, 1 J. Bourchier Av., 1164 Sofia, Bulgaria
3. Department of Microbiology, University of Food Technologies, 26 Maritza Blvd., 4002 Plovdiv, Bulgaria