1. Clinic of Endocrinology, University Hospital “Alexandrovska”, Department of Internal Medicine, Medical Faculty, Medical University—Sofia, Sofia, Bulgaria.
2. Clinic of Internal Diseases, Naval Hospital—Varna, Military Medical Academy, Bulgaria.
3. Clinical Laboratory and Clinical Pharmacology, University Hospital “Alexandrovska”, Department of Clinical Laboratory, Medical University—Sofia, Sofia, Bulgaria.
4. Clinic of Rheumatology, University Hospital “St. Marina”, First Department of Internal Medicine, Medical Faculty, Medical University—Varna, Varna, Bulgaria.