1. Headache Group, Department of Basic and Clinical Neurosciences, King’s College London, London, United Kingdom
2. Neurocentro Svizzera Italiana, Centro Cefalea, Ospedale Civico Lugano, Ente Ospedaliero Cantonale, (EOC), Lugano, Switzerland
3. Department of Neurology, Copenhagen University Hospital – Herlev and Gentofte, Herlev, Denmark
4. Department of Neurology, Danish Headache Center, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
5. Department of Clinical Medicine, Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark
6. Department of Neurology, St. Olavs Hospital, Trondheim, Norway
7. NorHEAD, NTNU, Norwegian University of Science and Technology, Trondheim, Norway
8. Headache Clinic, IRCCS Neuromed, Pozzilli, Italy
9. Danish Knowledge Center on Headache Disorders, Rigshospitalet Glostrup, Glostrup, Denmark
10. IMTEL, Norwegian University of Science and Technology, Trondheim, Norway
11. Faculty of Biomedical Sciences, Universita della Svizzera Italiana, Lugano, Switzerland