1. Jefferson Headache Center, Thomas Jefferson University Hospital, Philadelphia, PA, USA
2. Danish Headache Centre, Department of Neurology, University of Copenhagen, Glostrup Hospital, Glostrup, Denmark
3. Department of Neurology, Mayo Clinic, Scottsdale, AZ, USA
4. Department of Neurology, Cologne City Hospitals, Cologne, Germany
5. Department of Neurology, Albert Einstein College of Medicine and the Montefiore Headache Center, Bronx, NY, USA
6. Service of Neurology, University Hospital, Salamanca, Spain, and
7. Department of Neurology, National Yang-Ming University, School of Medicine, Taipei, Taiwan