1. Departments of Neurology, Universities of Essen;
2. Municipal Hospital, Fulda;
3. Neurological Practice, Naples;
4. Departments of Neurology, Universities of Vienna;
5. Departments of Neurology, Universities of Zrich;
6. Departments of Neurology, Universities of Kiel;
7. Institute for Numerical Statistics, Cologne;
8. Medical Department of 3M Medica, Borken
9. Migraine Clinic, Duisburg;