1. Merck & Co. Inc, Kenilworth, NJ, USA
2. Department of Neurology, Albert Einstein College of Medicine, Bronx, NY, USA
3. Montefiore Headache Center, Bronx, NY, USA
4. Department of Neurology, The Mayo Clinic, Scottsdale, AZ, USA
5. Department of Neurology, Stanford University Medical Center, Palo Alto, CA, USA