1. Dermatology, University Medical Center Groningen; University of Groningen; 9700 RB Groningen The Netherlands
2. Department of Medical Sciences, Clinical Unit of Occupational Medicine; University of Trieste; 34129 Trieste Italy
3. Faculty of Health Science; Jan Kochanowski University; 25-317 Kielce Poland
4. Department of Dermatology; Nofer Institute of Occupational Medicine; 90-950 Lodz Poland
5. Department of Medical Informatics, Biometry and Epidemiology; University of Erlangen/Nürnberg; 91054 Erlangen Germany