1 Basel Institute for Clinical Epidemiology and Biostatistics, Department of Clinical Research, University Hospital Basel and University of Basel, Basel, Switzerland.
2 Swiss Tropical and Public Health Institute (Swiss TPH), Basel, Switzerland.
3 University Medical Library, University of Basel, Basel, Switzerland.
4 Departments of Medical Oncology and of Haematology, University Hospital Basel and University of Basel, Basel, Switzerland.
5 Basel Institute for Clinical Epidemiology and Biostatistics, Department of Clinical Research, University Hospital Basel and University of Basel, Basel, Switzerland lars.hemkens@usb.ch.