1. University of Hamburg; Unit of Health Sciences and Education; Martin-Luther-King-Platz 6 Hamburg Germany D-20146
2. Witten/Herdecke University; School of Nursing Science, Faculty of Health; Stockumer Str. 12 Witten Germany D-58453
3. University of Lübeck; Nursing Research Group, Institute for Social Medicine; Ratzeburger Allee 160 Lübeck Germany D-23538