1 Department Community and Occupational Medicine, University Medical Center Groningen, University of Groningen, Ant. Deusinglaan 1, 9713 AV, Groningen, The Netherlands. j.p.van.dijk@umcg.nl.
2 Graduate School Kosice Institute for Society and Health, Kosice, Slovakia. j.p.van.dijk@umcg.nl.
3 Health of Vulnerable Groups, Olomouc University Society and Health Institute, Palacky University, Olomouc, Czech Republic. j.p.van.dijk@umcg.nl.