1. First Cardiology Clinic, Medical School, National and Kapodistrian University of Athens, Hippokration Hospital, Athens, Greece
2. Clinic for Internal Disease InterMedica, Hypertension Centre, Nis, Serbia
3. Nephrology Department, Hippokration Hospital, Athens, Greece
4. 2nd Propedeutic Department of Internal Medicine, Aristotle University, Thessaloniki, Greece
5. Veteran Affairs Medical Center and Georgetown University, Washington, D.C, United States