1. Department of Social Medicine and Healthcare Organization, Medical University – Varna, Varna, Bulgaria
2. Department of Hygiene and Epidemiology, Medical University – Varna, Varna, Bulgaria
3. Social Work, The University of Texas at Arlington, Arlington, TX, USA
4. Department of Internal Diseases, Medical University – Varna, Varna, Bulgaria
5. College for Health, Community, and Policy, Department of Social Work, University of Texas at San Antonio, San Antonio, TX, USA