Complementary medicine in Germany: a multi-centre cross-sectional survey on the usage by and the needs of patients hospitalized in university medical centers oleh Ann-Kathrin Lederer, Alexandra Baginski, Lena Raab, Stefanie Joos, Jan Valentini, Carina Klocke, Yvonne Samstag, Katrin Hübner, Ivana Andreeva, Thomas Simmet, Tatiana Syrovets, Susanne Hafner, Anna Freisinger, Maximilian Andreas Storz, Roman Huber