1. Athens Naval Hospital, Athens, Greece.
2. 251 General Airforce Hospital, Athens, Greece.
3. Metropolitan General Hospital, Headache Clinic, Athens, Greece.
4. Nikea General Hospital, Neurology Department, Athens, Greece.
5. 2nd IKA Hospital, Thessaloniki, Greece.
6. Papageorgiou General Hospital, Neurology Department, Thessaloniki, Greece.
7. Psychiatric Clinic Anagenissis, Larissa, Greece.
8. Agios Dimitrios Hospital, Headache Clinic, Thessaloniki, Greece.