1. Department of Pathology, Trakia University, Medical Faculty, Stara Zagora, Bulgaria
2. Department of General and Operative Surgery, Trakia University, Medical Faculty, Stara Zagora Bulgaria
3. Ward of Operative Surgery, University Hospital “Prof. D-r Stoyan Kirkovich”, Stara Zagora, Bulgaria
4. Complex Oncology Centre, Stara Zagora, Bulgaria
5. Department of Chemistry and Biochemistry, Medical Faculty, Trakia University, Stara Zagora, Bulgaria