1. Faculty of Mathematics and Natural Sciences, South-West University “Neofit Rilski”, Blagoevgrad 2700, Bulgaria
2. University of Library Studies and Information Technologies, Sofia 1784, Bulgaria
3. Department of Physiology and Pharmacology “Vittorio Erspamer”, University of Rome “La Sapienza”, Rome 00185, Italy
4. Faculty of Chemistry and Pharmacy, Sofia University “St. Kliment Ohridski”, Sofia 1164, Bulgaria