1. Rett Expertise Centre, Maastricht University Medical Centre and School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
2. Gemiva-SVG Groep, Gouda, The Netherlands
3. Department of Epidemiology, Maastricht University, Maastricht, The Netherlands
4. Telethon Kids Institute, Nedlands, Australia
5. School of Physiotherapy and Exercise Science, Curtin University, Bentley, Australia
6. Rett Expertise Centre, Maastricht University, Maastricht, The Netherlands
7. Department of Epidemiology, Care and Public Health Research Institute, Maastricht University, Maastricht, The Netherlands