1. Department of Dermatology and Allergology (promotional student), University of Bonn, Bonn, Germany
2. Department of Dermatology (Emeritus) Medical University of Vienna, Vienna, Austria
3. Department of Dermatology and Allergology, University of Bonn, Bonn, Germany
4. Privatklinik Confraternität, Wien, Austria
5. Medizinische Universität Wien, Zentrum für Public Health, Abteilung für Umwelthygiene und Umweltmedizin, Wien, Austria
6. Department of Dermatology and Allergology (Emeritus), University of Bonn, Bonn, Germany
7. Private Practice Phlebology & Dermatology, Bonn, Germany and Department of Dermatology, University of Cologne, Köln, Germany