1. Chair of Complementary and Integrative Medicine, University of Duisburg-Essen, Knappschafts-Krankenhaus, Am Deimelsberg 34A, 45276 Essen, Germany
2. Karl und Veronica Carstens Foundation, 45276 Essen, Germany
3. Department of Palliative Care, University of Bonn, 53127 Bonn, Germany
4. Department of Integrative and Complementary Medicine, Institute for Social Medicine, Epidemiology and Health Economics, Immanuel Hospital Berlin, Charité University Medical Centre Berlin, 14109 Berlin, Germany
5. Department of Community Medicine, The National Research Centre in Complementary and Alternative Medicine (NAFKAM), University of Tromsø, 9037 Tromsø, Norway