1. Medical Faculty, Trakia University, Stara Zagora, Bulgaria
2. Independent Researcher, Cornwall, UK
3. Department of Hygiene, Epidemiology, Microbiology, Parasitology and Infectious Diseases, Medical Faculty, Trakia University, Stara Zagora, Bulgaria
4. Department of Special Surgery, Medical Faculty, Trakia University, Stara Zagora, Bulgaria
5. Department of Physical and Rehabilitation Medicine, Medical Faculty, Trakia University, Stara Zagora, Bulgaria