1. School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, L3 3AF Liverpool, England
2. College of Veterinary Medicine, The University of Tennessee, 2407 River Drive, Knoxville, Tennessee 37996-4500, United States
3. Laboratory of Mathematical Chemistry (LMC), As. Zlatarov University, Bourgas 8000, Bulgaria