1. Amsterdam Rehabilitation Research Center/Reade, PO box 58271, 1040 HG Amsterdam, the Netherlands.
2. University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, A. Deusinglaan 1, gebouw 3215. Groningen 9713 AV Groningen, the Netherlands.
3. Brain Center Rudolf Magnus and Center of Excellence in Rehabilitation Medicine, De Hoogstraat Rehabilitation and University Medical Center Utrecht, Rembrandtkade 10 3583 TM Utrecht, the Netherlands.
4. Center for Rehabilitation, Department of Rehabilitation Medicine, University of Groningen, University Medical Center Groningen, Hanzeplein 1. Fonteinstraat 4 9713 GZ Groningen, the Netherlands.
5. Rehabilitation Center Roessingh, Enschede, the Netherlands.