1. Charité Universitätsmedizin, Berlin, Germany.
2. Hospital Ruber Internacional, Madrid, Spain.
3. Universität Duisburg-Essen, Essen, Germany.
4. Centro Cefalee della Donna, Torino, Italy.
5. University Hospital of North Staffordshire, Stoke-on-Trent, UK.
6. Estimate Medical Statistics, Doesburg, the Netherlands.
7. University Witten/Herdecke, Witten, Germany.
8. Janssen-Cilag EMEA, Neuss, Germany.
9. Janssen-Cilag EMEA, Tilburg, the Netherlands.