1. Medical University of Plovdiv,Department of Epidemiology and Disaster Medicine,Plovdiv,Bulgaria
2. Medical University of Plovdiv,Department of Otorhinolaryngology,Plovdiv,Bulgaria
3. Medical University of Plovdiv,Department of Special Surgery,Plovdiv,Bulgaria
4. Medical University of Plovdiv,Department of Nursing Care,Plovdiv,Bulgaria