1. Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany.
2. Department of Neurological Surgery and Goodman Campbell Brain and Spine, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana.
3. Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P.R. China.
4. Department of Physical and Theoretical Chemistry, University of Regensburg, Regensburg, Germany.